French mathematician Henri whose famous conjecture was finally proven in 2003

• French mathematician Henri whose conjecture was one of the great unsolved problems (until it was cracked in 2003)
• French president: 1913-1920

Wikipedia Word definitions in Wikipedia
Poincaré is a French surname. Notable people with the surname include: Henri Poincaré (1854–1912), physicist, mathematician and philosopher of science Lucien Poincaré (1862–1920), physicist, brother of Raymond and cousin of Henri Raymond Poincaré (1860–1934), ...