login
A175738
Sizes of successive increasing gaps between 2-pseudoprimes.
4
220, 460, 756, 780, 1140, 1356, 1496, 2000, 3050, 3580, 4532, 4784, 5220, 7140, 12132, 20412, 20650, 22320, 26076, 39424, 42392, 65740, 81252, 87698, 137104, 164448, 203506, 370396, 484140, 491526, 506940, 667908, 682820, 777224, 951114, 1201538
OFFSET
1,1
COMMENTS
Rotkiewicz proves that a(n) < A175736(n)^2, and that the exponent can be replaced by 1 + epsilon for large enough n.
REFERENCES
A. Rotkiewicz, "Les intervalles contenants les nombres pseudopremiers", Rendiconti del Circolo Matematico di Palermo, Series 2, 14 (1965), pp. 278-280.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..207
H. Halberstam and A. Rotkiewicz, A gap theorem for pseudoprimes in arithmetic progression, Acta Arithmetica 13 (1967/1968), pp. 395-404.
Eric Weisstein's World of Mathematics, Fermat Pseudoprime
FORMULA
a(n) = A175737(n) - A175736(n).
CROSSREFS
Cf. A001567 (2-pseudoprimes), A175736 (lower end), A175737 (upper end).
Sequence in context: A287011 A333929 A157107 * A260203 A184543 A234558
KEYWORD
nonn,nice
AUTHOR
STATUS
approved