A357140 Number of n X n triangular (0,1)-matrices with exactly 2n entries equal to 1 and no zero rows or columns.

1, 0, 0, 1, 26, 865, 39268, 2375965, 185974145, 18337523130, 2227232055239, 327003956573263, 57121908284696448, 11712143532463633752, 2786114854266411595229, 761208643373263480081077, 236761580851204534640426709, 83183218467008383189955036015

Offset: 0

Author

Alois P. Heinz, Sep 14 2022

Keywords

• nonn

Crossrefs

Cf. A137252.

Formula

a(n) = A137252(2n,n).