Duplicate of A046729.

A089498

Duplicate of A046729.

Terms

    a(0) =0a(1) =4a(2) =20a(3) =120a(4) =696a(5) =4060a(6) =23660a(7) =137904a(8) =803760a(9) =4684660a(10) =27304196a(11) =159140520

External references