Coefficients of ménage hit polynomials.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =6a(5) =20a(6) =134a(7) =915a(8) =7324a(9) =65784a(10) =657180a(11) =7223637a(12) =86637650a(13) =1125842556a(14) =15757002706a(15) =236298742375