a(n) = (4*n^2 + 2*n - 3)*(2*n - 1)*n/3.

Terms

a(0) =0a(1) =1a(2) =34a(3) =195a(4) =644a(5) =1605a(6) =3366a(7) =6279a(8) =10760a(9) =17289a(10) =26410a(11) =38731a(12) =54924a(13) =75725a(14) =101934a(15) =134415a(16) =174096a(17) =221969a(18) =279090a(19) =346579a(20) =425620a(21) =517461a(22) =623414a(23) =744855a(24) =883224a(25) =1040025a(26) =1216826a(27) =1415259a(28) =1637020a(29) =1883869