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

Author

Amarnath Murthy, Sep 11 2003

Keywords

• nonn

Comments

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

Examples

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

Links

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

Crossrefs

A127582 is identical except for a(1).

Programs

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

Formula

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

Extensions

More terms from Ray Chandler, Sep 14 2003

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