1/3 of the number of permutations of 2 indistinguishable copies of 1..n with exactly 4 local maxima.

A152496

1/3 of the number of permutations of 2 indistinguishable copies of 1..n with exactly 4 local maxima.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =113a(4) =16565a(5) =1216902a(6) =65819156a(7) =3026987243a(8) =126794945523

External references