OFFSET
1,2
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
Seiichi Manyama, Aug 15 2019
EXTENSIONS
a(8) from Michael S. Branicky, Sep 05 2024
STATUS
approved