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A058220 Ultra-useful primes: smallest k such that 2^(2^n) - k is prime. 3
1, 3, 5, 15, 5, 59, 159, 189, 569, 105, 1557, 2549, 2439, 13797, 25353, 5627, 24317 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

2^(2^16)-5627 was found by Joel Levy in Feb 2004. - Donovan Johnson, Sep 13 2008

LINKS

Table of n, a(n) for n=1..17.

MATHEMATICA

np[n_]:=Module[{x=2^(2^n)}, x-NextPrime[x, -1]]; Array[np, 17] (* Harvey P. Dale, Jun 04 2011 *)

CROSSREFS

Cf. A058221.

Sequence in context: A270688 A270453 A270464 * A100181 A180620 A277323

Adjacent sequences:  A058217 A058218 A058219 * A058221 A058222 A058223

KEYWORD

nonn,hard,nice

AUTHOR

Warren D. Smith, Nov 30 2000

EXTENSIONS

a(16)-a(17) from Donovan Johnson, Sep 13 2008

STATUS

approved

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Last modified January 28 09:52 EST 2020. Contains 331319 sequences. (Running on oeis4.)