a(n) = n*(n^4 + 10*n^3 + 35*n^2 + 50*n + 144)/120.

Terms

a(0) =2a(1) =8a(2) =24a(3) =60a(4) =131a(5) =258a(6) =469a(7) =800a(8) =1296a(9) =2012a(10) =3014a(11) =4380a(12) =6201a(13) =8582a(14) =11643a(15) =15520a(16) =20366a(17) =26352a(18) =33668a(19) =42524a(20) =53151a(21) =65802a(22) =80753a(23) =98304a(24) =118780a(25) =142532a(26) =169938a(27) =201404a(28) =237365a(29) =278286