a(n) = (n^2-1)*(2*n^2-1).

Terms

a(0) =1a(1) =0a(2) =21a(3) =136a(4) =465a(5) =1176a(6) =2485a(7) =4656a(8) =8001a(9) =12880a(10) =19701a(11) =28920a(12) =41041a(13) =56616a(14) =76245a(15) =100576a(16) =130305a(17) =166176a(18) =208981a(19) =259560a(20) =318801a(21) =387640a(22) =467061a(23) =558096a(24) =661825a(25) =779376a(26) =911925a(27) =1060696a(28) =1226961