G.f. A(x) satisfies: A(x) = 1 + x * A(x^3/(1 - x)^3) / (1 - x)^3.

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =11a(5) =21a(6) =42a(7) =87a(8) =189a(9) =432a(10) =1018a(11) =2415a(12) =5694a(13) =13297a(14) =30768a(15) =70626a(16) =161011a(17) =364977a(18) =823536a(19) =1851706a(20) =4152972a(21) =9298653a(22) =20800758a(23) =46516437a(24) =104044590a(25) =232856189a(26) =521601174a(27) =1169670645a(28) =2626188319a(29) =5904269526