A373659 a(n) = A050446(n, n) = A050447(n, n).

1, 2, 6, 30, 190, 1547, 15106, 173502, 2286648, 34053437, 565424068, 10358963615, 207582616995, 4516836844067, 106059101583274, 2673073911292478, 71978776046880670, 2062324447652722085, 62647209605811093549, 2011144064488835839006, 68034719732835699646658

Offset: 0

Author

Peter Luschny, Jun 12 2024

Keywords

• nonn

Crossrefs

A050446, A050447, A373660.

Programs

Python

from functools import cache
@cache
def T(n, k):
    return T(n, k - 1) + sum(T(2 * j, k - 1) * T(n - 1 - 2 * j, k)
    for j in range(1 + (n - 1) // 2)) if k > 0 else 1
def a(n): return T(n, n)
print([a(n) for n in range(21)])

Formula

a(n) = A373660(n, 0).