Number of graphs with n nodes and n edges.

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =2a(5) =6a(6) =21a(7) =65a(8) =221a(9) =771a(10) =2769a(11) =10250a(12) =39243a(13) =154658a(14) =628635a(15) =2632420a(16) =11353457a(17) =50411413a(18) =230341716a(19) =1082481189a(20) =5228952960a(21) =25945377057a(22) =132140242356a(23) =690238318754