a(n) = (n^2 - n + 1)*(n^2 + n + 1).

Terms

a(0) =1a(1) =3a(2) =21a(3) =91a(4) =273a(5) =651a(6) =1333a(7) =2451a(8) =4161a(9) =6643a(10) =10101a(11) =14763a(12) =20881a(13) =28731a(14) =38613a(15) =50851a(16) =65793a(17) =83811a(18) =105301a(19) =130683a(20) =160401a(21) =194923a(22) =234741a(23) =280371a(24) =332353a(25) =391251a(26) =457653a(27) =532171a(28) =615441a(29) =708123