A357141 Number of n X n triangular matrices with nonnegative integer entries and without zero rows or columns such that sum of all entries is equal to 2n.
1, 1, 6, 71, 1433, 44443, 1968580, 118159971, 9240555677, 913352224942, 111374887418013, 16428282185046946, 2883740893056526715, 594152447495864629867, 142006380268368661423424, 38973735372090120549251580, 12174162204364698538764222978, 4294569227671480526607187583713
Offset: 0
Keywords
Crossrefs
Cf. A137251.
Formula
a(n) = A137251(2n,n).