Bisection of A000125.

Terms

a(0) =1a(1) =4a(2) =15a(3) =42a(4) =93a(5) =176a(6) =299a(7) =470a(8) =697a(9) =988a(10) =1351a(11) =1794a(12) =2325a(13) =2952a(14) =3683a(15) =4526a(16) =5489a(17) =6580a(18) =7807a(19) =9178a(20) =10701a(21) =12384a(22) =14235a(23) =16262a(24) =18473a(25) =20876a(26) =23479a(27) =26290a(28) =29317a(29) =32568