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