A152809 Column 4 of triangle A152798; a(n) = A152798(n+4,4).
1, 1, 5, 15, 49, 180, 685, 2748, 11683, 52262, 245357, 1207538, 6217803, 33428738, 187323142, 1092328063, 6618105311, 41600580908, 270931087106, 1825820975565, 12716770294407, 91437668751232, 678020392413506, 5179601279549207
Offset: 0