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

Terms

a(0) =1a(1) =9a(2) =61a(3) =260a(4) =927a(5) =2578a(6) =5965a(7) =12066a(8) =22135a(9) =37678a(10) =60457a(11) =92488a(12) =136043a(13) =193650a(14) =268093a(15) =362412a(16) =479903a(17) =624118a(18) =798865a(19) =1008208a(20) =1256467a(21) =1548218a(22) =1888293a(23) =2281780a(24) =2734023a(25) =3250622a(26) =3837433a(27) =4500568a(28) =5246395a(29) =6081538