G.f. A(x) satisfies: A(x) = 1 + x * A(x^4/(1 - x)^4) / (1 - x)^4.

Terms

a(0) =1a(1) =1a(2) =4a(3) =10a(4) =20a(5) =36a(6) =64a(7) =120a(8) =240a(9) =499a(10) =1060a(11) =2314a(12) =5252a(13) =12360a(14) =29632a(15) =70992a(16) =168096a(17) =392465a(18) =905940a(19) =2075314a(20) =4730052a(21) =10735516a(22) =24258688a(23) =54553000a(24) =122076240a(25) =271914499a(26) =603183508a(27) =1333268098a(28) =2937818900a(29) =6455143760