2041965

Appears in sequences

• The number of pairs of permutations in the product group S_n X S_n with k common descents, n >= 1 and 0 <= k <= n-1.at n=33A192721
• Triangle read by rows, (Sum_{k=0..n} T[n,k]*x^k) / (1-x)^(n+1) are generating functions of the columns of A287316.at n=39A287315
• Expansion of (1/x) * Series_Reversion( x * (1 - x) / (1 + x^2 / (1 - x)^2) ).at n=11A389410