Number of permutations p of {1,2,3,...,2n} such that Sum_{k=1..2n} abs(k-p(k)) = 2n.

A072948

Number of permutations p of {1,2,3,...,2n} such that Sum_{k=1..2n} abs(k-p(k)) = 2n.

Terms

    a(0) =1a(1) =1a(2) =7a(3) =46a(4) =327a(5) =2350a(6) =17222a(7) =127508a(8) =952299a(9) =7159090a(10) =54107670a(11) =410729140a(12) =3129241874a(13) =23914923644a(14) =183254996828

External references