Duplicate of A047772.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =8a(5) =42a(6) =232a(7) =1277a(8) =7183a(9) =41041a(10) =238315a(11) =1402076a(12) =8343804a(13) =50136483