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A152783 Values of p for which 2^p - 1 is prime and which are followed by a gap such that no 2^q - 1 is prime for p < q < 2*p. 0
127, 607, 4423, 216091, 1398269, 3021377 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..6.

FORMULA

{A000043(i): A134458(i) >= A000043(i)}. - R. J. Mathar, Dec 20 2008

EXAMPLE

127 is in this sequence because 2^127-1 is prime, but no value of 2^q-1 is prime for q > 127 and q <= 254. (The next value of q to yield a prime is 521 and is outside the (127,254] interval.)

MATHEMATICA

s={}; Do[If[MersennePrimeExponent[k+1] > 2 * MersennePrimeExponent[k], AppendTo[s, MersennePrimeExponent[k]]], {k, 1, 44}]; s (* Amiram Eldar, Feb 03 2019 *)

CROSSREFS

Cf. A000043, A134458.

Sequence in context: A096523 A299132 A142736 * A299890 A200813 A332574

Adjacent sequences:  A152780 A152781 A152782 * A152784 A152785 A152786

KEYWORD

nonn,more

AUTHOR

J. Lowell, Dec 12 2008

EXTENSIONS

Edited by R. J. Mathar, Dec 20 2008

a(5) inserted by Amiram Eldar, Feb 03 2019

STATUS

approved

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Last modified January 23 23:01 EST 2022. Contains 350515 sequences. (Running on oeis4.)