

A087522


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


15



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
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OFFSET

0,1


COMMENTS

Trivially the nth 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 3^13.
a(2) = 3 because 2^24.
a(3) = 7 because 2^38.


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



