Number of twice-partitions of n with no singletons.

Terms

a(0) =1a(1) =0a(2) =1a(3) =2a(4) =5a(5) =8a(6) =19a(7) =30a(8) =68a(9) =111a(10) =229a(11) =380a(12) =799a(13) =1280a(14) =2519a(15) =4325a(16) =8128a(17) =13666a(18) =25758a(19) =43085a(20) =79300a(21) =134571a(22) =240124a(23) =407794a(24) =730398a(25) =1224821a(26) =2152122a(27) =3646566a(28) =6338691a(29) =10657427