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A201914 Least prime p such that p+1 is divisible by 2^n and not by 2^(n+1). 3
2, 5, 3, 7, 47, 31, 191, 127, 1279, 3583, 5119, 6143, 20479, 8191, 81919, 294911, 1114111, 131071, 786431, 524287, 17825791, 14680063, 138412031, 109051903, 654311423, 1912602623, 738197503, 2818572287, 7247757311, 3758096383, 228707008511, 2147483647 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

See A126717 for the least k such that k*2^n-1 is prime.

LINKS

Donovan Johnson, Table of n, a(n) for n = 0..1000

MATHEMATICA

Table[k = 1; While[p = k*2^n - 1; ! PrimeQ[p], k = k + 2]; p, {n, 0, 40}]

CROSSREFS

Cf. A008864 (primes + 1), A057775 (p-1 case), A126717.

Sequence in context: A249162 A134563 A192178 * A021398 A186631 A182184

Adjacent sequences:  A201911 A201912 A201913 * A201915 A201916 A201917

KEYWORD

nonn

AUTHOR

T. D. Noe, Dec 27 2011

STATUS

approved

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Last modified July 23 22:18 EDT 2019. Contains 325269 sequences. (Running on oeis4.)