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 A090532 #5 Dec 05 2013 19:56:38 %S A090532 1,1,2,2,2,2,3,3,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,6,6,6, %T A090532 6,6,6,6,6,6,6,6,6,6,6,6,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,8,8,8,8, %U A090532 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9 %N A090532 Let f(n) = n - pi(n). Then a(n) = least number of steps such that f(f(...(n)))=1. %e A090532 a(10) = 3, 10 ->6 ->3 ->1. %e A090532 a(100) = 9. %e A090532 f(100) =100-25 = 75, f(75) = 75-21= 54, f(54) = 54-16 = 38, f(38) = 38-12= 26, f(26) = 26-9 = 17, f(17) = 17-7 = 10, f(10) = 10-4 =6, f(6) = 6-3=3, f(3) = 3-2 =1. %Y A090532 Cf. A025003. %K A090532 nonn %O A090532 2,3 %A A090532 _Amarnath Murthy_, Dec 07 2003 %E A090532 Corrected and extended by Sam Handler (sam_5_5_5_0(AT)yahoo.com), Dec 11 2004