Central terms of triangle A138271.

A138275

Central terms of triangle A138271.

Terms

    a(0) =1a(1) =2a(2) =18a(3) =268a(4) =5320a(5) =129474a(6) =3700550a(7) =121016160a(8) =4448701704a(9) =181463572394

External references