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

Author

Eric W. Weisstein

Keywords

• sign

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