Number of connectable 3 X n binary matrices.

Terms

a(0) =1a(1) =3a(2) =13a(3) =87a(4) =585a(5) =3899a(6) =25973a(7) =173039a(8) =1152849a(9) =7680691a(10) =51171485a(11) =340922567a(12) =2271346969a(13) =15132518507a(14) =100818201477a(15) =671686589663