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 A121952 #4 Mar 30 2012 17:25:49 %S A121952 3,22,194,1620,12982,98765,720519,5073805,34707100,231739037 %N A121952 Number of isomeric aza-benzenoids with four nitrogen atoms and n hexagons. %D A121952 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 A121952 If n=5 then the number of isomeric aza-benzenoids with four nitrogen atoms is 12982. Here n is the number of hexagons. %K A121952 nonn %O A121952 1,1 %A A121952 _Parthasarathy Nambi_, Sep 04 2006