Number of ways to place 4 nonattacking bishops on an n X n board.

Terms

a(0) =0a(1) =0a(2) =8a(3) =260a(4) =2728a(5) =16428a(6) =70792a(7) =242856a(8) =706048a(9) =1809464a(10) =4199064a(11) =8992684a(12) =18024072a(13) =34170724a(14) =61784632a(15) =107243472a(16) =179645376a(17) =291667440a(18) =460615272a(19) =709686228a(20) =1069477928a(21) =1579767068a(22) =2291594536a(23) =3269684088a(24) =4595235136