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A283191 Prime numbers p > 2 such that (2^p - 5)/3 is prime. 0
7, 13, 19, 31, 373, 811, 1117, 5059, 12601 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Let W = (2^p - 5)/3 and s = (W+1)/(2*p), then 5^s == 2 (mod W) for terms 1..9.

Subsequence of 7, 13, 19, 31, 51, 55, 85, 111, 319, 373,.. which are numbers m such that (2^m-5)/3 is prime. - R. J. Mathar, Mar 05 2017

LINKS

Table of n, a(n) for n=1..9.

MATHEMATICA

Select[Prime@ Range[2, 1000], PrimeQ[(2^# - 5)/3] &] (* Michael De Vlieger, Mar 03 2017 *)

PROG

(PARI)

forprime(p=3, 30000, W= (2^p-5)/3; if(ispseudoprime(W), print1(p, ", ")))

CROSSREFS

Cf. A000978.

Sequence in context: A023255 A122482 A265629 * A048375 A198035 A208720

Adjacent sequences:  A283188 A283189 A283190 * A283192 A283193 A283194

KEYWORD

nonn,more

AUTHOR

Dmitry Ezhov, Mar 02 2017

STATUS

approved

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Last modified May 20 23:05 EDT 2022. Contains 353886 sequences. (Running on oeis4.)