a(n) = n*(27*n^3 + 22*n^2 - 21*n - 16)/12.

Terms

a(0) =0a(1) =1a(2) =41a(3) =212a(4) =660a(5) =1585a(6) =3241a(7) =5936a(8) =10032a(9) =15945a(10) =24145a(11) =35156a(12) =49556a(13) =67977a(14) =91105a(15) =119680a(16) =154496a(17) =196401a(18) =246297a(19) =305140a(20) =373940a(21) =453761a(22) =545721a(23) =650992a(24) =770800a(25) =906425a(26) =1059201a(27) =1230516a(28) =1421812a(29) =1634585