OFFSET
1,1
LINKS
Daniel Starodubtsev, Table of n, a(n) for n = 1..10000
EXAMPLE
If a(n) = 109 then we find '1'109, '3'109, '7'109 and '9'109 to be primes.
PROG
(Python)
from sympy import isprime
print([i for i in range(800) if [isprime(int(j + str(i))) for j in '123456789'].count(True) == 4]) # Daniel Starodubtsev, Apr 11 2020
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, May 15 1998
STATUS
approved