Number defined by a recursive binary sequence

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In a math column in Scientific American many years ago, I encountered a peculiar binary sequence I describe below. Unfortunately I can't find a reference on this, so I would be grateful for any pointers or references.



Let $mathbbN$ be the set of positive integers and let $T = 2^n: nin mathbbNcup 0$ denote the set of powers of $2$. Let $textm:mathbbNto Tcup0$ be defined by $nmapsto maxbig(0cup tin T: t<nbig)$.



We define $a:mathbbNto0,1$ recursively by




  • $a(1) = 1$, and


  • $a(n) = 1-a(n-textm(n))$ for $ngeq 2$.

This sequence starts by $10010110ldots$ and I recall that it has some peculiar properties such as, no non-empty finite sub-sequence occurs $3$ times in a row.



Question. Is $sum_n=1^infty 2^-na(n)$ transcendent?










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    In a math column in Scientific American many years ago, I encountered a peculiar binary sequence I describe below. Unfortunately I can't find a reference on this, so I would be grateful for any pointers or references.



    Let $mathbbN$ be the set of positive integers and let $T = 2^n: nin mathbbNcup 0$ denote the set of powers of $2$. Let $textm:mathbbNto Tcup0$ be defined by $nmapsto maxbig(0cup tin T: t<nbig)$.



    We define $a:mathbbNto0,1$ recursively by




    • $a(1) = 1$, and


    • $a(n) = 1-a(n-textm(n))$ for $ngeq 2$.

    This sequence starts by $10010110ldots$ and I recall that it has some peculiar properties such as, no non-empty finite sub-sequence occurs $3$ times in a row.



    Question. Is $sum_n=1^infty 2^-na(n)$ transcendent?










    share|cite|improve this question























      up vote
      4
      down vote

      favorite









      up vote
      4
      down vote

      favorite











      In a math column in Scientific American many years ago, I encountered a peculiar binary sequence I describe below. Unfortunately I can't find a reference on this, so I would be grateful for any pointers or references.



      Let $mathbbN$ be the set of positive integers and let $T = 2^n: nin mathbbNcup 0$ denote the set of powers of $2$. Let $textm:mathbbNto Tcup0$ be defined by $nmapsto maxbig(0cup tin T: t<nbig)$.



      We define $a:mathbbNto0,1$ recursively by




      • $a(1) = 1$, and


      • $a(n) = 1-a(n-textm(n))$ for $ngeq 2$.

      This sequence starts by $10010110ldots$ and I recall that it has some peculiar properties such as, no non-empty finite sub-sequence occurs $3$ times in a row.



      Question. Is $sum_n=1^infty 2^-na(n)$ transcendent?










      share|cite|improve this question













      In a math column in Scientific American many years ago, I encountered a peculiar binary sequence I describe below. Unfortunately I can't find a reference on this, so I would be grateful for any pointers or references.



      Let $mathbbN$ be the set of positive integers and let $T = 2^n: nin mathbbNcup 0$ denote the set of powers of $2$. Let $textm:mathbbNto Tcup0$ be defined by $nmapsto maxbig(0cup tin T: t<nbig)$.



      We define $a:mathbbNto0,1$ recursively by




      • $a(1) = 1$, and


      • $a(n) = 1-a(n-textm(n))$ for $ngeq 2$.

      This sequence starts by $10010110ldots$ and I recall that it has some peculiar properties such as, no non-empty finite sub-sequence occurs $3$ times in a row.



      Question. Is $sum_n=1^infty 2^-na(n)$ transcendent?







      nt.number-theory reference-request real-analysis transcendental-number-theory transcendence






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      Dominic van der Zypen

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          Let $t(i)_0^infty$ be the Thue-Morse sequence. (It starts $0,1,1,0,1,0,0,1,ldots$.).



          I claim that your sequence is described by $a(n)=1-t(n-1)$ where $n$ is a positive integer. (It is similar to sequence A010059 in the OEIS, but its index starts at $1$ instead of at $0$.)



          The proof is as follows:



          For $n=1$, $a(1)=1-t(1-1)=1$. We now consider $nge 2$.



          From this OEIS link, let $A_k$ denote the first $2^k$ terms of $t$; then $A_0=0$ and for $kge 0$, $A_k+1=A_k,B_k$, where $B_k$ is obtained from $A_k$ by interchanging $0$'s and $1$'s. That is, $1-t(i)=t(i-2^k)$ where $2^kle ile 2^k+1-1$. Since $mathrmm(i)$ is the largest power of $2$ less than $i$, then $mathrmm(i+1)=2^k$. Thus, $1-t(i)=t(i-mathrmm(i+1))$. Letting $i=n-1$ yields $1-t(n-1)=t(n-1-mathrmm(n))$. Letting $a(n)=1-t(n-1)$ yields $a(n)=t(n-1-mathrmm(n))=1-(1-t(n-mathrmm(n)-1))=1-a(n-mathrmm(n))$. $blacksquare$




          The Prouhet-Thue-Morse constant $0.01101001ldots$ (in binary) (which is based on the Thue-Morse sequence) was shown to be transcendental by Kurt Mahler in 1929. It follows that the constant formed from your sequence is also transcendental.






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            down vote













            Let $t(i)_0^infty$ be the Thue-Morse sequence. (It starts $0,1,1,0,1,0,0,1,ldots$.).



            I claim that your sequence is described by $a(n)=1-t(n-1)$ where $n$ is a positive integer. (It is similar to sequence A010059 in the OEIS, but its index starts at $1$ instead of at $0$.)



            The proof is as follows:



            For $n=1$, $a(1)=1-t(1-1)=1$. We now consider $nge 2$.



            From this OEIS link, let $A_k$ denote the first $2^k$ terms of $t$; then $A_0=0$ and for $kge 0$, $A_k+1=A_k,B_k$, where $B_k$ is obtained from $A_k$ by interchanging $0$'s and $1$'s. That is, $1-t(i)=t(i-2^k)$ where $2^kle ile 2^k+1-1$. Since $mathrmm(i)$ is the largest power of $2$ less than $i$, then $mathrmm(i+1)=2^k$. Thus, $1-t(i)=t(i-mathrmm(i+1))$. Letting $i=n-1$ yields $1-t(n-1)=t(n-1-mathrmm(n))$. Letting $a(n)=1-t(n-1)$ yields $a(n)=t(n-1-mathrmm(n))=1-(1-t(n-mathrmm(n)-1))=1-a(n-mathrmm(n))$. $blacksquare$




            The Prouhet-Thue-Morse constant $0.01101001ldots$ (in binary) (which is based on the Thue-Morse sequence) was shown to be transcendental by Kurt Mahler in 1929. It follows that the constant formed from your sequence is also transcendental.






            share|cite|improve this answer


























              up vote
              3
              down vote













              Let $t(i)_0^infty$ be the Thue-Morse sequence. (It starts $0,1,1,0,1,0,0,1,ldots$.).



              I claim that your sequence is described by $a(n)=1-t(n-1)$ where $n$ is a positive integer. (It is similar to sequence A010059 in the OEIS, but its index starts at $1$ instead of at $0$.)



              The proof is as follows:



              For $n=1$, $a(1)=1-t(1-1)=1$. We now consider $nge 2$.



              From this OEIS link, let $A_k$ denote the first $2^k$ terms of $t$; then $A_0=0$ and for $kge 0$, $A_k+1=A_k,B_k$, where $B_k$ is obtained from $A_k$ by interchanging $0$'s and $1$'s. That is, $1-t(i)=t(i-2^k)$ where $2^kle ile 2^k+1-1$. Since $mathrmm(i)$ is the largest power of $2$ less than $i$, then $mathrmm(i+1)=2^k$. Thus, $1-t(i)=t(i-mathrmm(i+1))$. Letting $i=n-1$ yields $1-t(n-1)=t(n-1-mathrmm(n))$. Letting $a(n)=1-t(n-1)$ yields $a(n)=t(n-1-mathrmm(n))=1-(1-t(n-mathrmm(n)-1))=1-a(n-mathrmm(n))$. $blacksquare$




              The Prouhet-Thue-Morse constant $0.01101001ldots$ (in binary) (which is based on the Thue-Morse sequence) was shown to be transcendental by Kurt Mahler in 1929. It follows that the constant formed from your sequence is also transcendental.






              share|cite|improve this answer
























                up vote
                3
                down vote










                up vote
                3
                down vote









                Let $t(i)_0^infty$ be the Thue-Morse sequence. (It starts $0,1,1,0,1,0,0,1,ldots$.).



                I claim that your sequence is described by $a(n)=1-t(n-1)$ where $n$ is a positive integer. (It is similar to sequence A010059 in the OEIS, but its index starts at $1$ instead of at $0$.)



                The proof is as follows:



                For $n=1$, $a(1)=1-t(1-1)=1$. We now consider $nge 2$.



                From this OEIS link, let $A_k$ denote the first $2^k$ terms of $t$; then $A_0=0$ and for $kge 0$, $A_k+1=A_k,B_k$, where $B_k$ is obtained from $A_k$ by interchanging $0$'s and $1$'s. That is, $1-t(i)=t(i-2^k)$ where $2^kle ile 2^k+1-1$. Since $mathrmm(i)$ is the largest power of $2$ less than $i$, then $mathrmm(i+1)=2^k$. Thus, $1-t(i)=t(i-mathrmm(i+1))$. Letting $i=n-1$ yields $1-t(n-1)=t(n-1-mathrmm(n))$. Letting $a(n)=1-t(n-1)$ yields $a(n)=t(n-1-mathrmm(n))=1-(1-t(n-mathrmm(n)-1))=1-a(n-mathrmm(n))$. $blacksquare$




                The Prouhet-Thue-Morse constant $0.01101001ldots$ (in binary) (which is based on the Thue-Morse sequence) was shown to be transcendental by Kurt Mahler in 1929. It follows that the constant formed from your sequence is also transcendental.






                share|cite|improve this answer














                Let $t(i)_0^infty$ be the Thue-Morse sequence. (It starts $0,1,1,0,1,0,0,1,ldots$.).



                I claim that your sequence is described by $a(n)=1-t(n-1)$ where $n$ is a positive integer. (It is similar to sequence A010059 in the OEIS, but its index starts at $1$ instead of at $0$.)



                The proof is as follows:



                For $n=1$, $a(1)=1-t(1-1)=1$. We now consider $nge 2$.



                From this OEIS link, let $A_k$ denote the first $2^k$ terms of $t$; then $A_0=0$ and for $kge 0$, $A_k+1=A_k,B_k$, where $B_k$ is obtained from $A_k$ by interchanging $0$'s and $1$'s. That is, $1-t(i)=t(i-2^k)$ where $2^kle ile 2^k+1-1$. Since $mathrmm(i)$ is the largest power of $2$ less than $i$, then $mathrmm(i+1)=2^k$. Thus, $1-t(i)=t(i-mathrmm(i+1))$. Letting $i=n-1$ yields $1-t(n-1)=t(n-1-mathrmm(n))$. Letting $a(n)=1-t(n-1)$ yields $a(n)=t(n-1-mathrmm(n))=1-(1-t(n-mathrmm(n)-1))=1-a(n-mathrmm(n))$. $blacksquare$




                The Prouhet-Thue-Morse constant $0.01101001ldots$ (in binary) (which is based on the Thue-Morse sequence) was shown to be transcendental by Kurt Mahler in 1929. It follows that the constant formed from your sequence is also transcendental.







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                edited 1 hour ago

























                answered 4 hours ago









                Joel Reyes Noche

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