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 A087913 #3 Mar 30 2012 18:50:38 %S A087913 0,1,1,3,1,5,1,6,7,7,1,10,1,13,13,12,1,15,1,15,19,19,1,20,23,23,26,26, %T A087913 1,26,1,24,31,31,31,30,1,37,37,30,1,39,1,39,39,43,1,40,47,49,47,51,1, %U A087913 52,53,52,53,53,1,52,1,61,62,48,61,65,1,65,67,69,1,60,1,73,74,74,73 %N A087913 Greatest number less than n such that the number of prime factors is one less than that of n; a(1)=0. %C A087913 A001222(a(n)) = A001222(n) - 1 for n>1. %Y A087913 Cf. A079890. %K A087913 nonn %O A087913 1,4 %A A087913 _Reinhard Zumkeller_, Oct 26 2003