G.f.: 1/((1-x)*(1-x^2))^5.

Terms

a(0) =1a(1) =5a(2) =20a(3) =60a(4) =160a(5) =376a(6) =820a(7) =1660a(8) =3190a(9) =5830a(10) =10252a(11) =17380a(12) =28600a(13) =45760a(14) =71500a(15) =109252a(16) =163735a(17) =240955a(18) =348920a(19) =497640a(20) =700128a(21) =972400a(22) =1334840a(23) =1812200a(24) =2435420a(25) =3241628a(26) =4276520a(27) =5594360a(28) =7261040a(29) =9354080