a(n) = (4*n+3)*(4*n+7).

Terms

a(0) =21a(1) =77a(2) =165a(3) =285a(4) =437a(5) =621a(6) =837a(7) =1085a(8) =1365a(9) =1677a(10) =2021a(11) =2397a(12) =2805a(13) =3245a(14) =3717a(15) =4221a(16) =4757a(17) =5325a(18) =5925a(19) =6557a(20) =7221a(21) =7917a(22) =8645a(23) =9405a(24) =10197a(25) =11021a(26) =11877a(27) =12765a(28) =13685a(29) =14637