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

Terms

a(0) =1a(1) =18a(2) =75a(3) =196a(4) =405a(5) =726a(6) =1183a(7) =1800a(8) =2601a(9) =3610a(10) =4851a(11) =6348a(12) =8125a(13) =10206a(14) =12615a(15) =15376a(16) =18513a(17) =22050a(18) =26011a(19) =30420a(20) =35301a(21) =40678a(22) =46575a(23) =53016a(24) =60025a(25) =67626a(26) =75843a(27) =84700a(28) =94221a(29) =104430