Number of pairs of permutations of degree n that avoid (12,21).
A007767
Number of pairs of permutations of degree n that avoid (12,21).
Terms
- a(0) =1a(1) =1a(2) =3a(3) =17a(4) =151a(5) =1899a(6) =31711a(7) =672697a(8) =17551323a(9) =549500451a(10) =20246665349a(11) =864261579999
External references
- oeis: A007767