Number of semimodular lattices on n nodes.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =4a(6) =8a(7) =17a(8) =38a(9) =88a(10) =212a(11) =530a(12) =1376a(13) =3693a(14) =10232a(15) =29231a(16) =85906a(17) =259291a(18) =802308a(19) =2540635a(20) =8220218a(21) =27134483a(22) =91258141a(23) =312324027a(24) =1086545705a(25) =3838581926