G.f.: x^2/((1-x^2)^2*Product_{i>0}(1-x^i)).

Terms

a(0) =0a(1) =1a(2) =1a(3) =4a(4) =5a(5) =12a(6) =16a(7) =31a(8) =42a(9) =72a(10) =98a(11) =155a(12) =210a(13) =315a(14) =423a(15) =610a(16) =812a(17) =1136a(18) =1498a(19) =2047a(20) =2674a(21) =3585a(22) =4642a(23) =6125a(24) =7865a(25) =10240a(26) =13046a(27) =16791a(28) =21237a(29) =27060