Number of squares on infinite quarter chessboard at <=n knight moves from the corner.

Terms

a(0) =1a(1) =3a(2) =12a(3) =32a(4) =59a(5) =91a(6) =130a(7) =176a(8) =229a(9) =289a(10) =356a(11) =430a(12) =511a(13) =599a(14) =694a(15) =796a(16) =905a(17) =1021a(18) =1144a(19) =1274a(20) =1411a(21) =1555a(22) =1706a(23) =1864a(24) =2029a(25) =2201a(26) =2380a(27) =2566a(28) =2759a(29) =2959