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

Terms

a(0) =9a(1) =75a(2) =245a(3) =567a(4) =1089a(5) =1859a(6) =2925a(7) =4335a(8) =6137a(9) =8379a(10) =11109a(11) =14375a(12) =18225a(13) =22707a(14) =27869a(15) =33759a(16) =40425a(17) =47915a(18) =56277a(19) =65559a(20) =75809a(21) =87075a(22) =99405a(23) =112847a(24) =127449a(25) =143259a(26) =160325a(27) =178695a(28) =198417a(29) =219539