OFFSET
1,1
COMMENTS
a(n)=0 (mod 7) for n>6.
EXAMPLE
a(3)=1007 is included as 997, 907 and 7 are primes.
PROG
(PARI) a(n) = {m = 10^n; ok = 0; while (! ok, if (! isprime(m), ok = 1; for (k=1, n, if (! isprime(m-10^k), ok = 0; break; ); ); ); if (! ok, m++); ); return (m); } \\ Michel Marcus, Jul 16 2013
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Anton Vrba (antonvrba(AT)yahoo.com), Nov 29 2006
EXTENSIONS
a(9) and a(10) from Michel Marcus, Jul 16 2013
STATUS
approved