a(n) is the number of unlabeled rank-3 graded lattices with 4 coatoms and n atoms.

Terms

a(0) =1a(1) =4a(2) =13a(3) =34a(4) =68a(5) =121a(6) =197a(7) =299a(8) =432a(9) =600a(10) =806a(11) =1055a(12) =1352a(13) =1698a(14) =2100a(15) =2561a(16) =3085a(17) =3675a(18) =4338a(19) =5074a(20) =5891a(21) =6790a(22) =7777a(23) =8854a(24) =10029a(25) =11300a(26) =12677a(27) =14160a(28) =15756a(29) =17465