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A172461 Primes p such that 2*p-1 and 2^p-1 are both primes. 3
2, 3, 7, 19, 31, 607, 1279, 2281, 44497, 1257787, 13466917 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

a(1) = 2 is a term since it is a prime and 2^2 - 1 = 3 and 2*2 - 1 = 3 are primes.

a(2) = 3 is a term since it is a prime and 2^3 - 1 = 7 and 2*3 - 1 = 5 are primes.

MATHEMATICA

Select[MersennePrimeExponent[Range[47]], PrimeQ[2# -1] &] (* Amiram Eldar, Jul 29 2020 *)

CROSSREFS

Intersection of A000043 and A005382.

Cf. A000668.

Sequence in context: A152609 A298943 A340281 * A253971 A291339 A235616

Adjacent sequences:  A172458 A172459 A172460 * A172462 A172463 A172464

KEYWORD

nonn,more

AUTHOR

Juri-Stepan Gerasimov, Feb 03 2010, Feb 06 2010

EXTENSIONS

a(9)-a(11) from Robert G. Wilson v, Feb 26 2010

STATUS

approved

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Last modified October 23 21:27 EDT 2021. Contains 348217 sequences. (Running on oeis4.)