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 A174950 #4 Mar 30 2012 18:52:39 %S A174950 0,1,2,1,2,2,0,0,2,0,0,2,0,0,1,0,2,1,0,0,1,0,1,0,0,0,0,1,0,0,0,0,0,0, %T A174950 0,0,2,0,1,0,2,0,0,1,0,0,0,0,1,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,1,0,0,0, %U A174950 1,0,0,1,0,0,0,2,0,1,0,0,0,1,0,0,0,0,0,1,0,0,1,1,0,0,0,2,0,0,0,2,0,0,1,0,0 %N A174950 Size of sea of semiprimes surrounding n-th prime. %C A174950 Numbers of previous and following semiprimes of n-th prime. %e A174950 a(1)=0 because first prime is in a sea of 0 semiprimes; a(2)=1 because 2nd prime is in a sea of 1 semiprimes (3, 4); a(3)=2 because 3rd prime is in a sea of 2 semiprimes (4, 5, 6); a(4)=1 because 4th prime is in a sea of 1 semiprimes (6, 7); a(4)=2 because 5th prime is in a sea of 2 semiprimes (9, 10, 11). %Y A174950 Cf. A000040, A001358, A046930, A159461. %K A174950 nonn %O A174950 1,3 %A A174950 _Juri-Stepan Gerasimov_, Apr 02 2010 %E A174950 Corrected by _Ray Chandler_, Apr 06 2010