Diagonal matrix - All entries not on the main diagonal (the diagonal from the upper left to the lower right corner) are zero. Especially easy to raise to a power.
... producer (+ 1985)
April 3 - Sally Rand[?], dancer (+ 1979)
April 7 - Ralph Bunche[?], diplomat, winner of the Nobel Peace Prize
April 16 - Fifi D'Orsay, actress ...