Matrices with 2 rows.

Terms

a(0) =1a(1) =2a(2) =6a(3) =23a(4) =109a(5) =618a(6) =4096a(7) =31133a(8) =267219a(9) =2557502a(10) =27011734a(11) =312115953a(12) =3916844779a(13) =53053052462a(14) =771450742596