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 A179372 #2 Mar 31 2012 14:41:48 %S A179372 1,4,6,8,10,12,9,2,14,16,18,15,3,20,24,21,5,27,7,25,11,30,22,28,26,13, %T A179372 32,36,40,42,33,17,34,19,35,23,44,38,45,29,39,31,46,48,50,37,49,41,51, %U A179372 43,54,52,56,47,60,55,53,57,59,63,61,64,66,68,70,72,58,75,67,62,78,76 %N A179372 a(1) = 1; a(n) = smallest positive integer not already used which has a prime signature different from a(n-1), a(n-1)+1 and a(n-1)-1. %C A179372 A permutation of the positive integers. %e A179372 To compute a(8), we see a(7) is 9; we look for the smallest unused positive integer that does not have the same prime signature as either 8, 9 or 10. The first such number is 2. %Y A179372 Cf. A179371 %K A179372 nonn %O A179372 1,2 %A A179372 _Will Nicholes_, Jul 11 2010