A181492 - OEIS

A181492

Primes of the form p=3*2^k+1 such that p-2 is also a prime.

7, 13, 193, 786433

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OFFSET

1,1

COMMENTS

Sequence A181490 lists the exponents k, sequences A181491 and A181493 the corresponding lesser twin prime and their average.

a(5) > 3 * 2^3000 + 1. - Max Z. Scialabba, Dec 24 2023

LINKS

FORMULA

MATHEMATICA

Select[3 2^Range[100]+1, And@@PrimeQ[{#, #-2}]&] (* Harvey P. Dale, Jun 19 2013 *)

PROG

(PARI) for( k=1, 999, ispseudoprime(3<<k-1)|next; ispseudoprime(3<<k+1)|next; print1(3<<k+1, ", "))

CROSSREFS

KEYWORD

nonn

AUTHOR

M. F. Hasler, Oct 30 2010

STATUS

approved