2
$\begingroup$
  • Let $a(n)$ be A344960 (i.e., position of binary complement of $n$-th word in A341258). By definition, in order to calculate $a(n)$, we need to know A341258. Below we will correspond this sequence with the function $w(n)$.

  • To compute A341258, we also need to know a few additional features listed below.

  • Let $s(n)$ be A000201, $t(n)$ be A001950, $p(n)$ be A005206 and $q(n)$ be A060144.

  • Let $w(n)$ be $n$-th word in A341258. To reproduce the sequence from itself, start with $w(1)=0$, $w(2)=1$ and apply $w(n)=0w(p(n-1))$ if $n=s(p(n))$, $w(n)=1w(q(n-1))$ otherwise. Compare it with definition in A341258:

Let $s = (s(n))$ be a strictly increasing sequence of positive integers with infinite complement, $t = (t(n))$. For $n\geqslant1$, let $s'(n)$ be the number of $s(i)$ that are $\leqslant n-1$ and let $t'(n)$ be the number of $t(i)$ that are $\leqslant n-1$. Define $w(1) = 0$, $w(t(1)) = 1$, and $w(n) = 0w(s'(n))$ if $n$ is in $s$, and $w(n) = 1w(t'(n))$ if $n$ is in $t$. Then $(w(n))$ is the "s-induced ordering" of all $01$-words. $s$ = A000201; $t$ = A001950; $s'$ = A005206; $t'$ = A060144;

What does it mean? This means that we must first choose $s(n)$. In our case it is A000201. Then $t(n)$ is a complement of $s(n)$. Also $p(n)$ and $q(n)$ are closely related to $s'(n)$ and $t'(n)$, where we just change condition $\leqslant n-1$ to $\leqslant n$. So obviously $n$ is in $s$ if $s(p(n))=n$ and $n$ is in $t$ if $t(q(n))=n$. Since $t(n)$ is a compement of $s(n)$ we define second case as otherwise to first case.

  • Let $b(n)$ be A345253 (i.e., maximal Fibonacci tree: Arrangement of the positive integers as labels of a complete binary tree).

  • Let $c(n)$ be A353654 (i.e., numbers whose binary expansion has the same number of trailing $0$ bits as other $0$ bits).

  • Let $d(n)$ be A030109 (i.e., write $n$ in binary, reverse bits, subtract $1$, divide by $2$).

Sequence Machine conjectures (1, 2) that $$a(n) = b(d(c(n+2))) - 1.$$

Here is the PARI/GP program to check it numerically:

s(n) = (n + sqrtint(5*n^2))\2
t(n) = s(n) + n
p(n) = s(n+1) - n - 1
q(n) = n - p(n)
w(n) = if(n < 3, [n - 1], if(n==s(p(n)), concat(0, w(p(n-1))), concat(1, w(q(n-1)))))
a(n) = my(A = 0, v1); v1 = w(n); for(i=1, #v1, v1[i] = !v1[i]); until(w(A)==v1, A++); A
b(n) = my(x=0, y=0); for(i=0, logint(n, 2), [x, y]=[y+1, x+y]; if(bittest(n, i), [x, y]=[y, x+y])); y;
d(n) = fromdigits(Vecrev(binary(n)), 2)\2
isok(k) = if (k==1, 1, (logint(k-1, 2)-hammingweight(k-1) == valuation(k, 2)));
my(z=4); for(k=1,299, while(!(isok(z)), z++); print(b(d(z))-1==a(k)); z++;);

Is there a way to prove it?

$\endgroup$
5
  • 1
    $\begingroup$ Good question +1. I Think I have seen the conjecture before but unpublished and offline. Unless by mr Wolfram perhaps. $\endgroup$
    – mick
    Commented Apr 2 at 20:49
  • 1
    $\begingroup$ You ask a question about $a$, $b$, $c$, and $d$. So, what is the point of $s,t,p,q,w$? $\endgroup$ Commented Apr 3 at 0:22
  • 1
    $\begingroup$ @GerryMyerson, thank you for comment! To calculate $a(n)$, we need to know $w(n)$. Similarly, to calculate $w(n)$, we need to know $s(n)$, $t(n)$, $p(n)$ and $q(n)$. $\endgroup$ Commented Apr 3 at 5:39
  • 3
    $\begingroup$ These connections are not the least bit obvious from your post. Better to edit in all the connections here, instead of making everyone shuttle back and forth between here and OEIS. $\endgroup$ Commented Apr 3 at 5:44
  • $\begingroup$ @GerryMyerson, thank you for comment! Done. $\endgroup$ Commented Apr 3 at 6:31

0

You must log in to answer this question.