a(n) = (2*n+1)*(4*n+1).

Terms

a(0) =1a(1) =15a(2) =45a(3) =91a(4) =153a(5) =231a(6) =325a(7) =435a(8) =561a(9) =703a(10) =861a(11) =1035a(12) =1225a(13) =1431a(14) =1653a(15) =1891a(16) =2145a(17) =2415a(18) =2701a(19) =3003a(20) =3321a(21) =3655a(22) =4005a(23) =4371a(24) =4753a(25) =5151a(26) =5565a(27) =5995a(28) =6441a(29) =6903