G.f. satisfies: A(x) = (1+x)/(1-x) * A(x^2)*A(x^3)*A(x^4)*...*A(x^n)*... .

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =16a(5) =28a(6) =52a(7) =88a(8) =152a(9) =252a(10) =416a(11) =664a(12) =1076a(13) =1684a(14) =2636a(15) =4060a(16) =6248a(17) =9444a(18) =14292a(19) =21312a(20) =31748a(21) =46796a(22) =68804a(23) =100200a(24) =145784a(25) =210240a(26) =302520a(27) =432428a(28) =616716a(29) =873972