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A033809 Smallest m>0 such that (2n-1)2^m+1 is prime, or -1 if no such value exists. 6
1, 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; text; internal format)
OFFSET

1,4

COMMENTS

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

CROSSREFS

Cf. A046067 (except for initial term a(1) identical to this sequence), A046068, A046069, A046070.

Cf. A040076

Sequence in context: A128807 A309035 A071628 * A046067 A342416 A305531

Adjacent sequences:  A033806 A033807 A033808 * A033810 A033811 A033812

KEYWORD

sign

AUTHOR

Eric W. Weisstein

STATUS

approved

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Last modified July 16 14:52 EDT 2021. Contains 346065 sequences. (Running on oeis4.)