

A306751


Numbers k such that 9*10^(2*k) + 3*10^k + 1 are prime.


1




OFFSET

1,2


LINKS



EXAMPLE

13 is prime ==> a(1) = 0.
931 = 7^2 * 19.
90301 = 73 * 1237.
9003001 = 7 * 757 * 1699.
900030001 = 13 * 4969 * 13933.
90000300001 is prime ==> a(2) = 5.


PROG

(PARI) for(k=0, 1e3, if(ispseudoprime(9*100^k+3*10^k+1), print1(k", ")))


CROSSREFS



KEYWORD

nonn,base,more


AUTHOR



STATUS

approved



