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

Terms

a(0) =0a(1) =1a(2) =14a(3) =94a(4) =380a(5) =1135a(6) =2786a(7) =5964a(8) =11544a(9) =20685a(10) =34870a(11) =55946a(12) =86164a(13) =128219a(14) =185290a(15) =261080a(16) =359856a(17) =486489a(18) =646494a(19) =846070a(20) =1092140a(21) =1392391a(22) =1755314a(23) =2190244a(24) =2707400a(25) =3317925a(26) =4033926a(27) =4868514a(28) =5835844a(29) =6951155