Maximal length of rook tour on an n X n+2 board.

Terms

a(0) =4a(1) =16a(2) =38a(3) =78a(4) =136a(5) =220a(6) =330a(7) =474a(8) =652a(9) =872a(10) =1134a(11) =1446a(12) =1808a(13) =2228a(14) =2706a(15) =3250a(16) =3860a(17) =4544a(18) =5302a(19) =6142a(20) =7064a(21) =8076a(22) =9178a(23) =10378a(24) =11676a(25) =13080a(26) =14590a(27) =16214a(28) =17952a(29) =19812