a(n) = ((2*n + 1)^6 + 1)/2.

Terms

a(0) =1a(1) =365a(2) =7813a(3) =58825a(4) =265721a(5) =885781a(6) =2413405a(7) =5695313a(8) =12068785a(9) =23522941a(10) =42883061a(11) =74017945a(12) =122070313a(13) =193710245a(14) =297411661a(15) =443751841a(16) =645733985a(17) =919132813a(18) =1282863205a(19) =1759371881a(20) =2375052121a(21) =3160681525a(22) =4151882813