Averages of four consecutive odd squares.

Terms

a(0) =21a(1) =41a(2) =69a(3) =105a(4) =149a(5) =201a(6) =261a(7) =329a(8) =405a(9) =489a(10) =581a(11) =681a(12) =789a(13) =905a(14) =1029a(15) =1161a(16) =1301a(17) =1449a(18) =1605a(19) =1769a(20) =1941a(21) =2121a(22) =2309a(23) =2505a(24) =2709a(25) =2921a(26) =3141a(27) =3369a(28) =3605a(29) =3849