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 A255980 #13 Mar 23 2015 14:17:38 %S A255980 0,1,1,0,1,2,1,2,0,2,1,3,1,2,3,0,1,3,1,4,3,2,1,4,0,2,4,4,1,5,1,5,3,2, %T A255980 5,0,1,2,3,5,1,6,1,4,6,2,1,6,0,6,3,4,1,7,5,7,3,2,1,7,1,2,7,0,5,6,1,4, %U A255980 3,8,1,8,1,2,8,4,8,6,1,7,0,2,1,9,5,2,3 %N A255980 Number of iterations of A067565 required to reach a perfect square. %C A255980 Iterating A067565 will always result in a perfect square, because all fixed points are squares, and A067565(n) <= n all n. %C A255980 a(n) = 0 if and only if n is a perfect square. %C A255980 a(n) = 1 if and only if n is prime. %H A255980 Peter Kagey, <a href="/A255980/b255980.txt">Table of n, a(n) for n = 1..5000</a> %e A255980 Let g(n) = A067565(n) %e A255980 a(12) = 3 because g(g(g(12))) = g(g(6)) = g(3) = 0, which is a perfect square. %o A255980 (Ruby) %o A255980 def a(n) %o A255980 c = 0 %o A255980 n = a067565(n) while n.is_nonsquare? && c += 1 %o A255980 c %o A255980 end %Y A255980 Cf. A067565. %K A255980 nonn %O A255980 1,6 %A A255980 _Peter Kagey_, Mar 12 2015