a(n) = n*(n+1)^2*(2+n)*(3+2*n)*(19+8*n)/180.

Terms

a(0) =0a(1) =9a(2) =98a(3) =516a(4) =1870a(5) =5369a(6) =13132a(7) =28560a(8) =56772a(9) =105105a(10) =183678a(11) =306020a(12) =489762a(13) =757393a(14) =1137080a(15) =1663552a(16) =2379048a(17) =3334329a(18) =4589754a(19) =6216420a(20) =8297366a(21) =10928841a(22) =14221636a(23) =18302480a(24) =23315500a(25) =29423745a(26) =36810774a(27) =45682308a(28) =56267946a(29) =68822945