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 A290089 #13 Aug 08 2017 22:14:56 %S A290089 0,1,1,2,1,3,1,3,2,4,1,5,1,5,2,5,1,6,1,6,3,6,1,7,2,4,3,7,1,4,1,7,2,6, %T A290089 2,8,1,6,4,8,1,9,1,8,4,8,1,10,2,9,2,6,1,11,4,10,4,9,1,6,1,10,5,10,2,4, %U A290089 1,11,3,4,1,12,1,4,4,8,2,8,1,12,5,9,1,13,4,6,2,12,1,9,2,12,4,12,2,14,1,8,4,13,1,9,1,8,4 %N A290089 Filter-sequence for the prime signature of cototient: a(1) = 0; for n > 1, a(n) = A101296(A051953(n)). %H A290089 Antti Karttunen, <a href="/A290089/b290089.txt">Table of n, a(n) for n = 1..16384</a> %F A290089 a(1) = 0; for n > 1, a(n) = A101296(A051953(n)). %Y A290089 Cf. A051953, A101296, A277906, A290087. %Y A290089 Cf. A000040 (the positions of 1's), A050530 (the positions of 2's). %K A290089 nonn %O A290089 1,4 %A A290089 _Antti Karttunen_, Aug 07 2017