Sierpinski Number
In number theory, a Sierpinski or Sierpiński number is an odd natural number k such that k2n + 1 is composite, for all natural numbers n; in 1960, Wacław Sierpiński proved that there are infinitely many odd integers k which have this property.
In other words, when k is a Sierpinski number, all members of the following set are composite:
Numbers in such a set with odd k and k < 2n are Proth numbers.
Read more about Sierpinski Number: Known Sierpinski Numbers, The Sierpinski Problem
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