a(n) = (4*n+1)*(4*n+3)*(4*n+5).

Terms

a(0) =15a(1) =315a(2) =1287a(3) =3315a(4) =6783a(5) =12075a(6) =19575a(7) =29667a(8) =42735a(9) =59163a(10) =79335a(11) =103635a(12) =132447a(13) =166155a(14) =205143a(15) =249795a(16) =300495a(17) =357627a(18) =421575a(19) =492723a(20) =571455a(21) =658155a(22) =753207a(23) =856995a(24) =969903a(25) =1092315a(26) =1224615a(27) =1367187a(28) =1520415a(29) =1684683