A Størmer number is a positive integer  for which the greatest prime factor  of  is at least . Every Gregory number  can be expressed uniquely as a sum of s where the s are Størmer numbers. The first few Størmer numbers are given by Conway and Guy (1996) and Todd (1949) and are given by , 2, 4, 5, 6, 9, 10, 11, 12, 14, 15, 16, 19, 20, ... (OEIS A005528), corresponding to greatest prime factors 2, 5, 17, 13, 37, 41, 101, 61, 29, ... (OEIS A005529).

REFERENCES:

Conway, J. H. and Guy, R. K. "Størmer's Numbers." The Book of Numbers. New York: Springer-Verlag, pp. 245-248, 1996.

Sloane, N. J. A. Sequences A005528/M0950 and A005529/M1505 in "The On-Line Encyclopedia of Integer Sequences."

Todd, J. "A Problem on Arc Tangent Relations." Amer. Math. Monthly 56, 517-528, 1949.