56958988812domain: NAppears in sequencesMain diagonal of symmetric array defined by the recurrence T(n,1)=1, T(1,k)=1, for n >= k: T(n,k) = Sum_{i=1..k-1} T(n-i,k), for n < k: T(n,k) = Sum_{i=1..n-1} T(k-i,n).at n=20A212263