%I #12 Oct 01 2013 17:58:12
%S 3,5,7,11,13,43,4003,40000003,40000000003,
%T 40000000000000000000000000000000000000003
%N Primes of the form n*10^x + n - 1, where 0 < n < 9, x = 0,1,2,3...
%C The next 2 terms for x <= 1000 are 4*10^419+3 and 4*10^449+3 both PARI proved primes. Except for the first 5 terms, the outer digits of these numbers are 4 and 3. This follows from the fact that all other combinations produce multiples of 2,3 or 5.
%e n=4,x=3. a(x,n) = 4*10^3+4-1 = 4003 prime.
%o (PARI) n10nm1(n) = { local(x,y,k); for(x=0,n, for(k=1,8, y=10^x*k+k-1; if(isprime(y),print1(y",")) ) ) }
%K nonn
%O 1,1
%A _Cino Hilliard_, Jul 11, 2005
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