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 A121951 #4 Mar 30 2012 17:25:49 %S A121951 3,14,109,730,4918,32043,204417,1277866,7860506,47678819 %N A121951 Number of isomeric aza-benzenoids with three nitrogen atoms and n hexagons. %D A121951 N. Trinajstich, Z. Jericevic, J. V. Knop, W. R. Muller and K. Szymanski, "Computer generation of isomeric structures", Pure and Appl. Chem., vol. 55 (1983) pp. 379-390. %e A121951 If n=5 then the number of isomeric aza-benzenoids with three nitrogen atoms is 4918. Here n is the number of hexagons. %K A121951 nonn %O A121951 1,1 %A A121951 _Parthasarathy Nambi_, Sep 04 2006