a(n) = 16n^4 + 64n^3 + 104n^2 + 80n + 21.

Terms

a(0) =21a(1) =285a(2) =1365a(3) =4221a(4) =10197a(5) =21021a(6) =38805a(7) =66045a(8) =105621a(9) =160797a(10) =235221a(11) =332925a(12) =458325a(13) =616221a(14) =811797a(15) =1050621a(16) =1338645a(17) =1682205a(18) =2088021a(19) =2563197a(20) =3115221a(21) =3751965a(22) =4481685a(23) =5313021a(24) =6254997a(25) =7317021a(26) =8508885a(27) =9840765a(28) =11323221