Number of nX6 0..1 arrays with each 1 adjacent to 3 or 6 king-move neighboring 1s.

Terms

a(0) =1a(1) =9a(2) =23a(3) =45a(4) =162a(5) =479a(6) =1198a(7) =3534a(8) =10374a(9) =28464a(10) =80600a(11) =233023a(12) =663259a(13) =1871905a(14) =5398412a(15) =15702374a(16) =44643584a(17) =130054976a(18) =387536847a(19) =1118773498a(20) =3332947080a(21) =10271834711a(22) =30432525534a(23) =93816278500a(24) =301779073626a(25) =927540514785