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A212488 Smallest k>0 such that (5^n-k)*5^n-1 and (5^n-k)*5^n+1 are a twin prime pair or 0 if no such k exists. 2
0, 1, 11, 1, 17, 85, 17, 25, 71, 25, 83, 673, 3623, 1069, 401, 1225, 1361, 409, 3449, 2581, 779, 613, 605, 781, 395, 5797, 17, 6967, 755, 361, 3443, 5467, 6857, 679, 53, 9355, 3287, 2941, 22385, 6091, 8423, 685, 13649, 2437, 113, 19393, 19781, 12253, 53603, 21049, 5321, 2149, 21779 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Conjecture: There is always one such k if n>1.

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..501

PROG

(PFGW64 and SCRIPTIFY)

SCRIPT

DIM nn, 1

DIM kk

DIM jj

DIMS tt

OPENFILEOUT myfile, a(n).txt

OPENFILEOUT myf, b(n).txt

LABEL loopn

SET nn, nn+1

SET jj, 0

IF nn>500 THEN END

SET kk, -1

LABEL loopk

SET kk, kk+2

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

PRP (5^nn-kk)*5^nn-1, tt

IF ISPRP THEN GOTO a

IF ISPRIME THEN GOTO a

GOTO loopk

LABEL a

SET jj, jj+1

PRP (5^nn-kk)*5^nn+1, tt

IF ISPRP THEN GOTO d

IF ISPRIME THEN GOTO d

GOTO loopk

LABEL d

WRITE myfile, tt

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

WRITE myf, tt

GOTO loopn

CROSSREFS

Cf. A212487

Sequence in context: A280506 A222803 A201132 * A178243 A040131 A282868

Adjacent sequences:  A212485 A212486 A212487 * A212489 A212490 A212491

KEYWORD

nonn

AUTHOR

Pierre CAMI, Jul 18 2012

STATUS

approved

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Last modified December 6 09:25 EST 2019. Contains 329791 sequences. (Running on oeis4.)