Number of twice-partitions of n with no (1)'s.

Terms

a(0) =1a(1) =0a(2) =2a(3) =3a(4) =9a(5) =13a(6) =38a(7) =56a(8) =144a(9) =237a(10) =524a(11) =886a(12) =1961a(13) =3225a(14) =6700a(15) =11702a(16) =23007a(17) =39787a(18) =77647a(19) =133707a(20) =254896a(21) =442736a(22) =820703a(23) =1427446a(24) =2630008a(25) =4535330a(26) =8224819a(27) =14250148a(28) =25513615a(29) =43981753