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A046069 Smallest m >= 0 such that (2n-1)2^m-1 is prime, or -1 if no such value exists. +0
7
2, 0, 2, 1, 1, 2, 3, 1, 2, 1, 1, 4, 3, 1, 4, 1, 2, 2, 1, 3, 2, 7, 1, 4, 1, 1, 2, 1, 1, 12, 3, 2, 4, 5, 1, 2, 7, 1, 2, 1, 3, 2, 5, 1, 4, 1, 3, 2, 1, 1, 10, 3, 2, 10, 9, 2, 8, 1, 1, 12, 1, 2, 2, 25, 1, 2, 3, 1, 2, 1, 1, 2, 5, 1, 4, 5, 3, 2, 1, 1, 2, 3, 2, 4, 1, 2, 2, 1, 1, 8, 3, 4, 2, 1, 3, 226, 3, 1, 2 (list; graph; listen)
OFFSET

1,1

COMMENT

There exist odd integers 2k-1 such that (2k-1)2^n-1 is always composite.

REFERENCES

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..1000

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

CROSSREFS

Cf. A046067, A046070.

Bisection of A040081.

Adjacent sequences: A046066 A046067 A046068 this_sequence A046070 A046071 A046072

Sequence in context: A112022 A000586 A029399 this_sequence A055651 A079627 A061398

KEYWORD

nonn

AUTHOR

Eric Weisstein (eric(AT)weisstein.com)

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Last modified July 4 09:27 EDT 2009. Contains 160562 sequences.


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