a(n) = (n^4 + 2n^3 + 5n^2 + 4)/4.

Terms

a(0) =1a(1) =3a(2) =14a(3) =46a(4) =117a(5) =251a(6) =478a(7) =834a(8) =1361a(9) =2107a(10) =3126a(11) =4478a(12) =6229a(13) =8451a(14) =11222a(15) =14626a(16) =18753a(17) =23699a(18) =29566a(19) =36462a(20) =44501a(21) =53803a(22) =64494a(23) =76706a(24) =90577a(25) =106251a(26) =123878a(27) =143614a(28) =165621a(29) =190067