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A213884 For the smallest k >= 1, the smallest single-digit j such that (10^k-j)*10^n-1 is prime. 3
1, 4, 1, 2, 2, 5, 1, 2, 1, 2, 1, 4, 4, 5, 5, 1, 4, 7, 1, 4, 2, 4, 4, 1, 2, 8, 7, 4, 1, 1, 2, 1, 1, 4, 7, 4, 1, 1, 7, 4, 8, 2, 7, 4, 8, 8, 7, 2, 2, 1, 8, 2, 8, 5, 7, 1, 8, 4, 8, 1, 4, 1, 4, 7, 1, 2, 8, 2, 4, 1, 4, 8, 4, 5, 8, 2, 1, 2, 7, 7, 5, 1, 4, 8, 7, 4, 1, 4, 2, 2, 4, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

These j are the associated shifts to be paired with the k-values of A213883. There are no multiples of 3 here, as explained in A213883.

For the first 2200 values of n, there is always at least one pair (k,j) that delivers a prime with the conditions.

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..2200

EXAMPLE

j=1 associated with the prime 89, j=4 associated with 599, j=1 associated with 8999, j=2 with 79999 are the first 4 entries.

MAPLE

A213884 := proc(n)

    for k from 1 do

        for j from 0 to 9 do

            if isprime( (10^k-j)*10^n-1) then

                return j;

            end if;

        end do:

    end do:

    return 0 ;

end proc: # R. J. Mathar, Jul 20 2012

PROG

SCRIPT

DIM nn, 0

DIM jj

DIM kk

DIMS tt

OPENFILEOUT myfile, a(n).txt

LABEL loopn

SET nn, nn+1

IF nn>2200 THEN END

SET kk, 0

LABEL loopk

SET kk, kk+1

IF kk>2*nn THEN GOTO loopn

SET jj, 0

LABEL loopj

SET jj, jj+1

IF jj%3==0 THEN SET jj, jj+1

IF jj>9 THEN GOTO loopk

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

PRP (10^kk-jj)*10^nn-1, tt

IF ISPRP THEN GOTO a

IF ISPRIME THEN GOTO a

GOTO loopj

LABEL a

WRITE myfile, tt

GOTO loopn

CROSSREFS

Cf. A213883.

Sequence in context: A106437 A279605 A054713 * A117021 A222213 A010473

Adjacent sequences:  A213881 A213882 A213883 * A213885 A213886 A213887

KEYWORD

nonn

AUTHOR

Pierre CAMI, Jun 29 2012

STATUS

approved

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Last modified July 4 12:08 EDT 2022. Contains 355075 sequences. (Running on oeis4.)