A230259 Sequence of pairs k>0 and j>1 with the smallest j and the smallest sum j+k such that (k*j^n-1)*k*j^n-1 is prime.

2, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 3, 1, 3, 2, 2, 1, 2, 1, 2, 8, 3, 5, 3, 3, 4, 1, 7, 1, 5, 4, 2, 2, 2, 1, 2, 1, 4, 1, 3, 7, 3, 2, 4, 5, 4, 1, 5, 2, 3, 3, 2, 2, 6, 2, 4, 1, 15, 1, 11, 10, 2, 5, 2, 3, 7, 3, 3, 1, 3, 1, 3, 2, 2, 1, 2, 17, 2, 5, 4, 7, 3, 5, 4, 4, 2, 2, 2, 1, 2, 5, 2, 8, 2, 4, 2, 2, 2, 1, 2, 8, 7, 5, 7, 4, 4, 1, 4, 4, 2, 2, 2, 1, 2, 17, 5, 14, 7, 2, 7, 3, 14, 6, 6, 1, 6, 3, 10, 3, 4, 3, 23, 3, 7, 12, 4, 3, 4

Offset

1,1

Links

Pierre CAMI, Table of n, a(n) for n = 1..4000

Example

Sequence starts with 2,2 as (2*2^1-1)*2*2^1-1=11 is prime and (1*2^1-1)*1*2^1-1 is unity.
(1*2^2-1)*1*2^2-1=11 prime so the second pair is 1,2.

Prog

PFGW & SCRIPTIFY
SCRIPT
DIM n, 0
DIM j
DIM k
DIM ss
DIMS tt
OPENFILEOUT myf, a(n).txt
LABEL a
SET n, n+1
IF n>2000 THEN END
SET ss, 2
LABEL b
SET ss, ss+1
SET j, 1
LABEL c
SET j, j+1
SET k, ss-j
IF k<1 THEN GOTO b
SETS tt, %d, %d, %d\,; n; k; j
PRP (k*j^n-1)*k*j^n-1, tt
IF ISPRP THEN GOTO d
GOTO c
LABEL d
WRITE myf, tt
GOTO a

Crossrefs

Cf. A156051, A227903.

Sequence in context: A128853 A136165 A134193 * A085030 A078377 A291454

Adjacent sequences: A230256 A230257 A230258 * A230260 A230261 A230262

Keyword

nonn

Author

Pierre CAMI, Oct 14 2013

Status

approved