Number of partitions of n into parts of exactly 2 sorts which are introduced in ascending order.

Terms

a(0) =1a(1) =4a(2) =12a(3) =30a(4) =72a(5) =160a(6) =351a(7) =743a(8) =1561a(9) =3219a(10) =6616a(11) =13456a(12) =27312a(13) =55139a(14) =111166a(15) =223472a(16) =448902a(17) =900305a(18) =1804838a(19) =3615137a(20) =7239325a(21) =14490368a(22) =29000050a(23) =58025059a(24) =116090823a(25) =232234573a(26) =464554483a(27) =929220024a(28) =1858618215a(29) =3717468189