a(n) = ((2*n+1)^8 + 1)/2.

Terms

a(0) =1a(1) =3281a(2) =195313a(3) =2882401a(4) =21523361a(5) =107179441a(6) =407865361a(7) =1281445313a(8) =3487878721a(9) =8491781521a(10) =18911429681a(11) =39155492641a(12) =76293945313a(13) =141214768241a(14) =250123206481a(15) =426445518721a(16) =703204309121