Number of unlabeled loop-graphs with n vertices and at most n edges.

Terms

a(0) =1a(1) =2a(2) =5a(3) =13a(4) =36a(5) =102a(6) =313a(7) =994a(8) =3318a(9) =11536a(10) =41748a(11) =156735a(12) =609973a(13) =2456235a(14) =10224216a(15) =43946245a(16) =194866898a(17) =890575047a(18) =4190997666a(19) =20289434813a(20) =100952490046a(21) =515758568587