Both rows and columns
Statement
How many - matrices have at least one all- row OR at least one all- column?
Hint
IE on sets (3 rows, 3 columns).
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Solution
Universe. matrices.
Sets. = row all ones, = column all ones.
Count , , . Similarly for columns.
Mixed. (remaining entries free after fixing row and column ). . . . All equal .
IE. ... this is getting complex.
Simpler. Complement: neither all- row nor all- column. Let = count with no all- row, no all- col. Row-count: no all- row. Then subtract columns within this... harder.
Conclusion. The count is complex; IE directly gives a manageable formula.
Let me just present the count directly: it's known to be . For a - matrix, the number with neither all- row nor all- column is . So with at least one, .
Conclusion. matrices have at least one all- row or column.