Number of inequivalent ways (mod D_4) three checkers can be placed on an n X n board.

Terms

a(0) =0a(1) =1a(2) =16a(3) =77a(4) =319a(5) =920a(6) =2397a(7) =5278a(8) =10874a(9) =20355a(10) =36390a(11) =61171a(12) =99441a(13) =154882a(14) =235179a(15) =346060a(16) =499172a(17) =702933a(18) =974124a(19) =1324585a(20) =1777555a(21) =2349116a(22) =3070441a(23) =3962762a(24) =5066814a(25) =6409975a(26) =8044322a(27) =10004463a(28) =12355749a(29) =15141190