Number of ways to place 4n nonattacking kings on a vertical cylinder 8 X 2n.

Terms

a(0) =32a(1) =256a(2) =1220a(3) =4460a(4) =13932a(5) =39316a(6) =103508a(7) =259372a(8) =626780a(9) =1473764a(10) =3392964a(11) =7682812a(12) =17166476a(13) =37942900a(14) =83115188a(15) =180699980a(16) =390351420a(17) =838619524a(18) =1793087780a(19) =3817890076a(20) =8099228012a(21) =17125372436a(22) =36104600340a(23) =75916936300a(24) =159249370652a(25) =333329766436