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 A107621 #3 Mar 30 2012 17:26:16 %S A107621 4,9,10,21,22,39,34,57,46,87,62,111,82,129,94,159,118,183,134,213,146, %T A107621 237,166,267,194,303,206,321,218,339,254,393,274,417,298,453,314,489, %U A107621 334,519,358,543,382,579,394,597,422,669,454,687 %N A107621 Primes multiplied alternately by 2 and 3. %C A107621 Cf. A107620 Primes multiplied alternately by 3 and 2. %F A107621 A107621(n) = prime(n)*(3 - mod(n, 2)). %t A107621 A107621[n_]:= Prime[n] (3 - Mod[n, 2]) %Y A107621 Cf. A107620. %K A107621 easy,nonn %O A107621 1,1 %A A107621 _Zak Seidov_, May 18 2005