A213884 For the smallest k >= 1, the smallest single-digit j such that (10^k-j)*10^n-1 is prime.

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

Offset: 1

Author

Pierre CAMI, Jun 29 2012

Keywords

• nonn

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.

Examples

			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.
		

Links

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

Crossrefs

Cf. A213883.

Programs

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