a(n) = n*(n+1)*(n+2)*(n+3)/6.

Terms

a(0) =0a(1) =4a(2) =20a(3) =60a(4) =140a(5) =280a(6) =504a(7) =840a(8) =1320a(9) =1980a(10) =2860a(11) =4004a(12) =5460a(13) =7280a(14) =9520a(15) =12240a(16) =15504a(17) =19380a(18) =23940a(19) =29260a(20) =35420a(21) =42504a(22) =50600a(23) =59800a(24) =70200a(25) =81900a(26) =95004a(27) =109620a(28) =125860a(29) =143840