Number of ways to place 4 non-attacking ferses on an n X n board.

Terms

a(0) =0a(1) =0a(2) =29a(3) =661a(4) =6285a(5) =35378a(6) =143787a(7) =468529a(8) =1301351a(9) =3202970a(10) =7170593a(11) =14872997a(12) =28969129a(13) =53527866a(14) =94568255a(15) =160741233a(16) =264175507a(17) =421511954a(18) =655152581a(19) =994751765a(20) =1478979173a(21) =2157585442a(22) =3093803379a(23) =4367119121a(24) =6076449375a(25) =8343762538a(26) =11318183177