a(n) = (3*n^5 - 35*n^4 + 145*n^3 - 235*n^2 + 152*n + 30)/30.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =9a(5) =18a(6) =59a(7) =190a(8) =513a(9) =1186a(10) =2435a(11) =4566a(12) =7977a(13) =13170a(14) =20763a(15) =31502a(16) =46273a(17) =66114a(18) =92227a(19) =125990a(20) =168969a(21) =222930a(22) =289851a(23) =371934a(24) =471617a(25) =591586a(26) =734787a(27) =904438a(28) =1104041a(29) =1337394