a(n) = n*(n+1)*(n+2)*(n+7)/24.

Terms

a(0) =0a(1) =2a(2) =9a(3) =25a(4) =55a(5) =105a(6) =182a(7) =294a(8) =450a(9) =660a(10) =935a(11) =1287a(12) =1729a(13) =2275a(14) =2940a(15) =3740a(16) =4692a(17) =5814a(18) =7125a(19) =8645a(20) =10395a(21) =12397a(22) =14674a(23) =17250a(24) =20150a(25) =23400a(26) =27027a(27) =31059a(28) =35525a(29) =40455