a(n) = (n^4 + 2*n^3 - n^2)/2.

Terms

a(0) =0a(1) =1a(2) =14a(3) =63a(4) =184a(5) =425a(6) =846a(7) =1519a(8) =2528a(9) =3969a(10) =5950a(11) =8591a(12) =12024a(13) =16393a(14) =21854a(15) =28575a(16) =36736a(17) =46529a(18) =58158a(19) =71839a(20) =87800a(21) =106281a(22) =127534a(23) =151823a(24) =179424a(25) =210625a(26) =245726a(27) =285039a(28) =328888a(29) =377609