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 A173073 #3 Mar 30 2012 18:52:39 %S A173073 0,0,2,3,4,4,4,5,6,6,6,7,8,8,8,9,9,9,9,9,10,11,11,11,11,11,12,12,12, %T A173073 13,14,14,14,15,15,15,15,15,16,16,16,16,16,17,18,18,18,18,18,19,19,19, %U A173073 20,21,21,21,21,21,22,22,22,23,23,23,23,23,24,24,24,24,24,24,24,25,25,25 %N A173073 (n-th nonnegative nonprime) minus (n-1). %C A173073 Zero together with (natural nonprimes minus n). %F A173073 a(n)=A141468(n)-A001477(n-1). [corrected _R. J. Mathar_, Apr 25 2010] %Y A173073 Cf. A001477, A073425, A141468. %K A173073 nonn %O A173073 1,3 %A A173073 _Juri-Stepan Gerasimov_, Feb 09 2010 %E A173073 Formula index corrected by _R. J. Mathar_, Apr 24 2010