A046067 - OEIS

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A046067

Smallest m such that (2n-1)2^m+1 is prime, or -1 if no such value exists.

0, 1, 1, 2, 1, 1, 2, 1, 3, 6, 1, 1, 2, 2, 1, 8, 1, 1, 2, 1, 1, 2, 2, 583, 2, 1, 1, 4, 2, 5, 4, 1, 1, 2, 1, 3, 2, 1, 3, 2, 1, 1, 4, 2, 1, 8, 2, 1, 2, 1, 3, 16, 1, 3, 6, 1, 1, 2, 3, 1, 8, 6, 1, 2, 3, 1, 4, 1, 3, 2, 1, 53, 6, 8, 3, 4, 1, 1, 8, 6, 3, 2, 1, 7, 2, 8, 1, 2, 2, 1, 4, 1, 3, 6, 1, 1, 2, 4, 15, 2 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,4`
	COMMENTS	`There exist odd integers 2k-1 such that (2k-1)2^n+1 is always composite.` `The smallest known example is 78557. Therefore a(39279) = -1.`
	REFERENCES	`John R. Cowles and Ruben Gamboa, Verifying Sierpinski and Riesel Numbers in ACL2, Arxiv preprint arXiv:1110.4671, 2011` `Ribenboim, P. The New Book of Prime Number Records. New York: Springer-Verlag, pp. 357-359, 1996.`
	LINKS	`T. D. Noe, Table of n, a(n) for n=1..5000 (with help from the Sierpinski problem website)` `Ray Ballinger and Wilfrid Keller, Sierpinski Problem` `Seventeen or Bust, A Distributed Attack on the Sierpinski Problem` `Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.` `Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.`
	CROSSREFS	`Cf. A046068.` `Bisection of A040076. Cf. A033809.` `Cf. A057192.` `Sequence in context: A128807 A071628 A033809 * A132066 A102190 A138650` `Adjacent sequences: A046064 A046065 A046066 * A046068 A046069 A046070`
	KEYWORD	`sign`
	AUTHOR	`Eric Weisstein (eric(AT)weisstein.com)`

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Last modified February 16 13:12 EST 2012. Contains 205909 sequences.