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 A137228 #2 Mar 30 2012 18:49:09 %S A137228 3,5,7,9,11,12,14,16,18,19,21,23,24,26,28,29,31,33,34,36,38,39,41,42, %T A137228 44,46,47,49,51,52,54,55,57,59,60,62,63,65,67,68,70,71,73,75,76,78,79, %U A137228 81,83,84,86,87,89,90,92,94,95,97,98,100,102,103,105,106,108,109,111,113 %N A137228 Minimal total number of edges in a polyiamond consisting of n triangular cells. %F A137228 a(n) = (3n + A067628(n))/2. %Y A137228 Cf. A135708, A067628, A000577. %K A137228 nonn %O A137228 1,1 %A A137228 _Tanya Khovanova_, Mar 07 2008