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A210651 a(n)=least odd number k such that 3*k*2^n-1 is a prime number 4
1, 1, 1, 1, 5, 1, 1, 9, 15, 5, 1, 29, 3, 5, 3, 15, 5, 1, 17, 19, 3, 11, 23, 13, 19, 19, 7, 9, 15, 71, 5, 19, 49, 1, 11, 15, 7, 1, 21, 39, 5, 11, 1, 19, 55, 11, 71, 39, 23, 29, 7, 61, 49, 15, 1, 11, 17, 37, 15, 31, 23, 19, 3, 1, 33, 21, 37, 21, 17, 9, 41, 43, 5, 7, 25, 1, 19, 37, 23, 5, 27, 5, 37, 31, 15, 85, 67, 43, 79, 77 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..7725

MAPLE

A210651 := proc(n)

        for k from 1 by 2 do

                if isprime(3*k*2^n-1) then

                        return k;

                end if;

        end do:

end proc: # R. J. Mathar, Mar 29 2012

PROG

PFGW64 and SCRIPTIFY from Primeform group

Command: pfgw64 -f in.txt

in.txt file :

SCRIPT

DIM nn, 0

DIM kk

DIMS tt

OPENFILEOUT myfile, a(n).txt

LABEL loopn

SET nn, nn+1

IF nn>7725 THEN END

SET kk, -1

LABEL loopk

SET kk, kk+2

SETS tt, %d, %d\,; nn; kk

PRP 3*kk*2^nn-1, tt

IF ISPRP THEN GOTO a

IF ISPRIME THEN GOTO a

GOTO loopk

LABEL a

WRITE myfile, tt

GOTO loopn

CROSSREFS

Cf. A126717.

Sequence in context: A081578 A184883 A279003 * A255831 A188461 A188474

Adjacent sequences:  A210648 A210649 A210650 * A210652 A210653 A210654

KEYWORD

nonn

AUTHOR

Pierre CAMI, Mar 27 2012

STATUS

approved

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Last modified December 1 01:37 EST 2021. Contains 349426 sequences. (Running on oeis4.)