Permanent of a certain cyclic n X n (0,1) matrix.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =120a(6) =720a(7) =1854a(8) =4738a(9) =12072a(10) =30818a(11) =79118a(12) =204448a(13) =528950a(14) =1370674a(15) =3557408a(16) =9244418a(17) =24043990a(18) =62573616a(19) =162925614a(20) =424377730a(21) =1105703640a(22) =2881483458a(23) =7510389278a(24) =19577689120a(25) =51038756326a(26) =133066443346a(27) =346944079632a(28) =904622495746