Maximal length of rook tour on an n X n+3 board.

Terms

a(0) =8a(1) =24a(2) =54a(3) =102a(4) =174a(5) =270a(6) =396a(7) =556a(8) =756a(9) =996a(10) =1282a(11) =1618a(12) =2010a(13) =2458a(14) =2968a(15) =3544a(16) =4192a(17) =4912a(18) =5710a(19) =6590a(20) =7558a(21) =8614a(22) =9764a(23) =11012a(24) =12364a(25) =13820a(26) =15386a(27) =17066a(28) =18866a(29) =20786