a(n) = (6*n+1)*(6*n+3)*(6*n+5).

Terms

a(0) =15a(1) =693a(2) =3315a(3) =9177a(4) =19575a(5) =35805a(6) =59163a(7) =90945a(8) =132447a(9) =184965a(10) =249795a(11) =328233a(12) =421575a(13) =531117a(14) =658155a(15) =803985a(16) =969903a(17) =1157205a(18) =1367187a(19) =1601145a(20) =1860375a(21) =2146173a(22) =2459835a(23) =2802657a(24) =3175935a(25) =3580965a(26) =4019043a(27) =4491465a(28) =4999527a(29) =5544525