494902domain: NAppears in sequencesRelated to graded partially ordered sets.at n=6A001827Array read by antidiagonals: T(n,k) = n! * Sum_{s} 2^(Sum_{i=1..k-1} s(i)*s(i+1))/(Product_{i=1..k} s(i)!) where the sum is over all nonnegative compositions s of n into k parts.at n=61A361950