

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
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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*2^11=11 prime so p=5 for n=1.
2^2+5*2^21=23 prime so p=5 for n=2.
2^3+5*2^31=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^mm1, 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



