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 A361913 #33 Jul 25 2023 22:43:40 %S A361913 2,2,2,1,2,4,2,2,1,2,2,3,2,1,2,4,2,3,1,2,2,8,2,1,2,2,2,4,1,4,2,2,2,1, %T A361913 2,6,2,2,1,5,2,6,2,1,2,11,2,4,1,2,2,5,2,1,2,2,2,7,1,3,2,2,2,1,2,4,2,2, %U A361913 1,3,2,8,2,1,2,2,2,10,1,2,2,12,2,1,2,2 %N A361913 a(n) is the number of steps in the main loop of the Pollard rho integer factorization algorithm for n, with x=2, y=2 and g(x)=x^2-1. %C A361913 x=2 and y=2 are the minimum effective values for Pollard rho, but any x = y > 2 would give the same answer. %C A361913 n is in A217562 if gcd(n, a(n)) > 1. %C A361913 n is in A047201 if gcd(phi(n), a(n)) > 1, where phi is Euler's totient function. %H A361913 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PollardRhoFactorizationMethod.html">Pollard rho Factorization Method</a>. %H A361913 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pollard%27s_rho_algorithm">Pollard's rho algorithm</a> %o A361913 (Python) %o A361913 from gmpy2 import * %o A361913 def a(n): %o A361913 c,d,x,y,g = 0,1,2,2,lambda x:pow(x,2,n)-1 %o A361913 while d == 1: %o A361913 c,x,y =c+1,g(x),g(g(y)) %o A361913 d = gcd(abs(x-y), n) %o A361913 return c %Y A361913 Cf. A005563. %K A361913 nonn %O A361913 2,1 %A A361913 _Darío Clavijo_, Mar 29 2023