Number of permutations of the multiset {1,1,2,2,...,2n,2n} having exactly n ascents and no number smaller than k between the two occurrences of any number k.

A290306

Number of permutations of the multiset {1,1,2,2,...,2n,2n} having exactly n ascents and no number smaller than k between the two occurrences of any number k.

Terms

    a(0) =1a(1) =2a(2) =58a(3) =4400a(4) =644020a(5) =155357384a(6) =56041398784

External references