This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A372505 #7 May 04 2024 05:37:15
%S A372505 0,0,0,1,0,0,0,1,0,0,1,0,0,0,2,0,1,0,1,0,0,0,1,0,1,0,0,0,0,0,0,2,0,0,
%T A372505 0,0,0,0,1,1,0,0,2,1,1,0,1,0,0,0,0,0,1,0,0,1,0,0,0,1,0,0,0,0,0,1,1,0,
%U A372505 0,0,2,2,0,0,1,0,0,0,0,1,0,1,0,0,0,0,1
%N A372505 a(n) = log_2(A368473(n)).
%C A372505 The first position of k, for k = 0, 1, ..., is 1, 4, 15, 126, 1134, ..., which is the position of A085629(2^k) in A138302.
%H A372505 Amiram Eldar, <a href="/A372505/b372505.txt">Table of n, a(n) for n = 1..10000</a>
%F A372505 a(n) = log_2(A005361(A138302(n))).
%t A372505 f[n_] := Module[{p = Times @@ FactorInteger[n][[;; , 2]], e}, e = IntegerExponent[p, 2]; If[p == 2^e, e, Nothing]]; Array[f, 150]
%o A372505 (PARI) lista(kmax) = {my(p, e); for(k = 1, kmax, p = vecprod(factor(k)[, 2]); e = valuation(p, 2); if(p >> e == 1, print1(e, ", ")));}
%Y A372505 Cf. A005361, A085629, A138302, A368473.
%Y A372505 Cf. A369934, A370078, A372467, A372469.
%K A372505 nonn,easy
%O A372505 1,15
%A A372505 _Amiram Eldar_, May 04 2024