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%I #23 Jul 20 2012 15:21:24
%S 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,
%T 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,
%U 4,1,4,8,4,5,8,2,1,2,7,7,5,1,4,8,7,4,1,4,2,2,4,5
%N For the smallest k >= 1, the smallest single-digit j such that (10^k-j)*10^n-1 is prime.
%C 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.
%C For the first 2200 values of n, there is always at least one pair (k,j) that delivers a prime with the conditions.
%H Pierre CAMI, <a href="/A213884/b213884.txt">Table of n, a(n) for n = 1..2200</a>
%e 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.
%p A213884 := proc(n)
%p for k from 1 do
%p for j from 0 to 9 do
%p if isprime( (10^k-j)*10^n-1) then
%p return j;
%p end if;
%p end do:
%p end do:
%p return 0 ;
%p end proc: # _R. J. Mathar_, Jul 20 2012
%o SCRIPT
%o DIM nn, 0
%o DIM jj
%o DIM kk
%o DIMS tt
%o OPENFILEOUT myfile, a(n).txt
%o LABEL loopn
%o SET nn, nn+1
%o IF nn>2200 THEN END
%o SET kk, 0
%o LABEL loopk
%o SET kk, kk+1
%o IF kk>2*nn THEN GOTO loopn
%o SET jj, 0
%o LABEL loopj
%o SET jj, jj+1
%o IF jj%3==0 THEN SET jj, jj+1
%o IF jj>9 THEN GOTO loopk
%o SETS tt, %d, %d, %d\,; nn; kk; jj
%o PRP (10^kk-jj)*10^nn-1, tt
%o IF ISPRP THEN GOTO a
%o IF ISPRIME THEN GOTO a
%o GOTO loopj
%o LABEL a
%o WRITE myfile, tt
%o GOTO loopn
%Y Cf. A213883.
%K nonn
%O 1,2
%A _Pierre CAMI_, Jun 29 2012
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