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 A174215 #6 Mar 30 2012 18:52:53 %S A174215 2,1,1,1,1,6,2,1,1,1,1,1,1,1,1,1,1,1,13,1,1,1,5,2,2,1,1,1,1,1,1,1,1,1, %T A174215 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,31,1,1,1,1,1,1,1,1,1,1,1,1,1, %U A174215 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1 %N A174215 First differences of A174214. %C A174215 If a(n) is odd, then it is 1 or prime; if a(n) is even, then 2+a(n)/2 is prime. %H A174215 V. Shevelev, <a href="http://arXiv.org/abs/0912.4006">Theorems on twin primes-dual case</a>, arXiv:0912.4006 %F A174215 a(n) = A174214(n+1)-A174214(n). %Y A174215 Cf. A167495, A166945, A174214 %K A174215 nonn,easy %O A174215 9,1 %A A174215 _Vladimir Shevelev_, Mar 12 2010 %E A174215 Terms corrected, using the Mathar-Layman corrections of A174214, by _Vladimir Shevelev_, Mar 26 2010