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 A144774 #3 Mar 31 2012 10:28:53 %S A144774 0,1,2,1,4,5,6,1,4,9,10,7,12,13,14,1,16,8,18,12,20,21,22,8,7,25,5,19, %T A144774 28,29,30,1,32,33,34,11,36,37,38,17,40,41,42,28,24,45,46,11,17,19,50, %U A144774 35,52,11,54,26,56,57,58,40,60,61,33,1,64,65,66,46,68,69,70,12,72,73,31,52,76 %N A144774 Number of positive integers k less than n such that rad(k) < rad(n). %C A144774 a(n) = n - 1 if n is a product of distinct primes, since these have rad(n) = n. %e A144774 rad(1) = 1 and rad(2) = 2, so a(2) = 1. %e A144774 rad(4) is also 2, so a(4) = 1. %e A144774 rad(12) = 6. The integers k less than 12 for which rad(k) < 6 are 1, 2, 3, 4, 5, 8 and 9. a(12) = 7. %Y A144774 Cf. A007947 %K A144774 easy,nonn %O A144774 1,3 %A A144774 _Reikku Kulon_, Sep 21 2008