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 A339813 #5 Dec 19 2020 07:59:40
%S A339813 0,1,0,2,0,1,0,1,0,2,0,1,0,3,0,1,0,5,0,1,0,2,0,2,0,1,0,7,0,1,0,2,0,1,
%T A339813 0,6,0,1,0,1,0,4,0,1,0,2,0,1,0,2,0,1,0,5,0,3,0,1,0,2,0,1,0,4,0,1,0,2,
%U A339813 0,1,0,1,0,2,0,1,0,3,0,1,0,4,0,1,0,2,0,2,0,1,0,4,0,1,0,2,0,1,0,4,0,1,0,1,0
%N A339813 The exponent of the highest power of 2 dividing (A019565(n) - 1).
%C A339813 The 2-adic valuation of A339809(n).
%H A339813 Antti Karttunen, <a href="/A339813/b339813.txt">Table of n, a(n) for n = 1..65537</a>
%F A339813 a(n) = A007814(A339809(n)).
%o A339813 (PARI)
%o A339813 A019565(n) = { my(m=1, p=1); while(n>0, p = nextprime(1+p); if(n%2, m *= p); n >>= 1); (m); };
%o A339813 A339813(n) = valuation((A019565(n)-1),2);
%Y A339813 Cf. A007814, A339809, A339814 (bisection).
%K A339813 nonn
%O A339813 1,4
%A A339813 _Antti Karttunen_, Dec 18 2020