A087522 a(0) = 2; for n>=1, a(n) = smallest prime p such that p+1 is divisible by an n-th power > 1.

2, 2, 3, 7, 31, 31, 127, 127, 1279, 3583, 5119, 6143, 8191, 8191, 81919, 131071, 131071, 131071, 524287, 524287, 14680063, 14680063, 109051903, 109051903, 654311423, 738197503, 738197503, 2147483647, 2147483647, 2147483647, 2147483647

Offset

0,1

Comments

Trivially the n-th power under consideration is 2^n for n > 1.

Links

John Mason, using Robert Israel's data for A127582, Table of n, a(n) for n = 0..3310

Formula

a(n) << 37^n by Xylouris' improvement to Linnik's theorem. - Charles R Greathouse IV, Dec 10 2013

Example

a(1) = 2 because 3^1|3.
a(2) = 3 because 2^2|4.
a(3) = 7 because 2^3|8.

Prog

(PARI) okdivs(pp1, n) = fordiv(pp1, d, if ((d>1) && ispower(d, n), return (1))); 0
a(n) = {if (n == 0, return (2)); p = 2; while (! okdivs(p+1, n), p = nextprime(p+1)); return (p); } \\ Michel Marcus, Sep 14 2013

Crossrefs

A127582 is identical except for a(1).

Sequence in context: A077001 A180996 A307503 * A092970 A052449 A053413

Adjacent sequences: A087519 A087520 A087521 * A087523 A087524 A087525

Keyword

nonn

Author

Amarnath Murthy, Sep 11 2003

Extensions

More terms from Ray Chandler, Sep 14 2003

Edited by N. J. A. Sloane, Jul 03 2008

Status

approved