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

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

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