36519556domain: NAppears in sequencesa(n) = Sum_{k=0..10} binomial(n,k).at n=29A008863Number of 1-punctured staircase polygons (by perimeter) with a hole of perimeter 4.at n=18A055022a(n) = Sum_{k=0..n} binomial(3*n-1,k).at n=10A387033