A007670 Numbers n such that 2^n - 2^((n + 1)/2) + 1 is prime. (Formerly M2703)

3, 7, 47, 73, 79, 113, 151, 167, 239, 241, 353, 367, 457, 1367, 3041, 27529, 49207, 160423, 364289, 991961, 1203793, 1667321, 4792057

Offset

1,1

Comments

If A007670 is a proper subset of A057429, then 364289 & 991961 are the next two terms.

References

J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n=1..23.

J. Brillhart, Concerning the number 2^(2p)+1, p prime, Math. Comp. 16 (80) (1962) 424-430.

J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.

S. S. Wagstaff, Jr., The Cunningham Project

Prog

(PARI) is(n)=isprime(2^n-2^((n+1)/2)+1) \\ Charles R Greathouse IV, Feb 17 2017

Crossrefs

Cf. A006598.

Sequence in context: A231893 A132565 A129518 * A263806 A074714 A064457

Adjacent sequences: A007667 A007668 A007669 * A007671 A007672 A007673

Keyword

nonn,hard,more

Author

N. J. A. Sloane, Robert G. Wilson v

Extensions

a(16)-a(18) from Robert G. Wilson v, Sep 07 2000

a(19)-a(23) from Serge Batalov, Jun 16 2020

Status

approved