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

Terms

a(0) =0a(1) =20a(2) =136a(3) =444a(4) =1040a(5) =2020a(6) =3480a(7) =5516a(8) =8224a(9) =11700a(10) =16040a(11) =21340a(12) =27696a(13) =35204a(14) =43960a(15) =54060a(16) =65600a(17) =78676a(18) =93384a(19) =109820a(20) =128080a(21) =148260a(22) =170456a(23) =194764a(24) =221280a(25) =250100a(26) =281320a(27) =315036a(28) =351344a(29) =390340