Wacław Franciszek Sierpiński (1882 - 1969) Polish mathematician, best known for the Sierpiński triangle and the Sierpiński numbers.

Sierpiński studied physics and mathematics at the University of Warsaw, graduating in 1903, then went for a doctorate at university in Kraków. In 1908 he started teaching at the University of Lwów. A prolific author of books and papers, Sierpiński wrote on many subjects but focused on irrational numbers and set theory. During World War I, Sierpiński was stuck in Russia, but the experience proved useful when he returned to Poland and helped his comrades break Russian cryptography. During this time he also founded and edited the journal Fundamenta Mathematicae. From 1929 to the end of his life, he received various honors at home and abroad. In 1964, he was elected to the London Mathematical Society.

In 1954, Sierpiński published a French paper on some properties of Euler's totient function and the sum of divisors function in Bull. Acad. Polon. Sci. Cl. III 2 with Andrzej Schinzel, who a few years later co-authored with Erdős a paper on the “Distributions of the values of some arithmetical functions” in Acta Arithmetica 6, giving Sierpiński an Erdős number of 2.