Number of nonnesting permutations of the multiset {1,1,2,2,...,n,n} that avoid 123.

A382361

Number of nonnesting permutations of the multiset {1,1,2,2,...,n,n} that avoid 123.

Terms

    a(0) =1a(1) =4a(2) =17a(3) =82a(4) =406a(5) =2070a(6) =10729a(7) =56394a(8) =299646a(9) =1606816a(10) =8683562

External references