Number of permutations on [n] whose up-down signature has nonnegative partial sums and which have exactly three descents.

A321269

Number of permutations on [n] whose up-down signature has nonnegative partial sums and which have exactly three descents.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =604a(7) =7296a(8) =54746a(9) =330068a(10) =1756878a(11) =8641800a(12) =40298572a(13) =180969752a(14) =790697160a(15) =3385019968a(16) =14270283414a(17) =59457742524a(18) =245507935018

External references