18897709824domain: NAppears in sequencesa(n)=(2n)!*(sum{k=1...2n}1/k)/(2n+1).at n=7A114450Square array read by antidiagonals: T(m,n) = H(n,2*m)*(2*m)!/(2*m+2*n-1). H(0,m) = 1/m, for all positive integers m. H(n,m) = Sum_{k=1..m} H(n-1,k).at n=34A136205