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A205236 Least prime p > 3 such that 2^n + p*2^k - 1 is prime for some k with n/3 < k < n+1 4
5, 5, 5, 7, 5, 5, 5, 7, 5, 5, 5, 11, 5, 5, 5, 7, 5, 5, 5, 7, 5, 5, 5, 11, 5, 5, 5, 7, 5, 5, 5, 7, 5, 5, 5, 11, 5, 5, 5, 7, 5, 5, 5, 7, 5, 5, 13, 11, 5, 5, 5, 7, 5, 5, 5, 7, 5, 5, 11, 17, 7, 5, 5, 7, 5, 5, 5, 7, 5, 5, 5, 11, 7, 5, 5, 7, 5, 5, 7, 7, 11, 5, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The prime p seems to be < 31.

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..10800

EXAMPLE

2^1+5*2^1-1=11 prime so p=5 for n=1.

2^2+5*2^2-1=23 prime so p=5 for n=2.

2^3+5*2^3-1=47 prime so p=5 for n=3.

PROG

PFGW64 from Primeform group and SCRIPTIFY

Command : pfgw64 -f in.txt

in.txt file :

SCRIPT

DIM nn, 0

DIM mm

DIM kk

DIMS tt

OPENFILEOUT myfile, prem.txt

LABEL loopn

SET nn, nn+1

IF nn>10800 THEN END

SET kk, 2

LABEL loopk

SET kk, kk+1

SET mm, nn/3

LABEL loopm

SET mm, mm+1

IF mm>nn THEN GOTO loopk

SETS tt, %d, %d, %d\ ; nn; p(kk); mm

PRP 2^nn+p(kk)*2^mm-1, tt

IF ISPRIME THEN GOTO a

IF ISPRP THEN GOTO a

GOTO loopm

LABEL a

WRITE myfile, tt

GOTO loopn

CROSSREFS

Cf. A205237.

Sequence in context: A092279 A159002 A127934 * A266948 A176172 A204911

Adjacent sequences:  A205233 A205234 A205235 * A205237 A205238 A205239

KEYWORD

nonn

AUTHOR

Pierre CAMI, Jan 24 2012

STATUS

approved

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Last modified September 27 04:10 EDT 2021. Contains 347673 sequences. (Running on oeis4.)