Number of inequivalent (mod D_8) ways to place 4 nonattacking knights on an n X n board.

Terms

a(0) =1a(1) =6a(2) =66a(3) =609a(4) =3375a(5) =14181a(6) =47485a(7) =136085a(8) =342739a(9) =784059a(10) =1653033a(11) =3267471a(12) =6107271a(13) =10901405a(14) =18683285a(15) =30934341a(16) =49659915a(17) =77611995a(18) =118386689a(19) =176753639a(20) =258774303a(21) =372270981a(22) =526962861a(23) =735113445a(24) =1011678595a(25) =1375177451a(26) =1847843545a(27) =2456771055a(28) =3234056439