Coefficients of ménage hit polynomials.

Terms

a(0) =2a(1) =8a(2) =20a(3) =152a(4) =994a(5) =7888a(6) =70152a(7) =695760a(8) =7603266a(9) =90758872a(10) =1174753372a(11) =16386899368a(12) =245046377410