G.f.: x^2*(x+1)^2/(x^3+x^2-1)^2.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =3a(5) =6a(6) =9a(7) =14a(8) =22a(9) =32a(10) =48a(11) =70a(12) =101a(13) =146a(14) =208a(15) =296a(16) =419a(17) =590a(18) =829a(19) =1160a(20) =1619a(21) =2254a(22) =3130a(23) =4338a(24) =6000a(25) =8284a(26) =11419a(27) =15716a(28) =21600a(29) =29648