a(n) = [x^n] (x^5 + 5*x^4 + 4*x^3 - 3*x + 1)/(x^2 + 2*x - 1)^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =20a(5) =60a(6) =174a(7) =490a(8) =1352a(9) =3672a(10) =9850a(11) =26158a(12) =68892a(13) =180180a(14) =468454a(15) =1211730a(16) =3120400a(17) =8004144a(18) =20460402a(19) =52139990a(20) =132502180a(21) =335882988a(22) =849507230a(23) =2144114234a(24) =5401408344a(25) =13583493000a(26) =34105191146a(27) =85504030974a(28) =214070361260a(29) =535269125508