OFFSET
1,1
LINKS
Toshitaka Suzuki, Table of n, a(n) for n = 1..448
FORMULA
a(11) = 1199999 because 119, 1199, 11999 and 119999 are not primes.
PROG
(Python)
from itertools import count
from sympy import isprime
def A373859(n): return next(p for p in ((n+1)*10**m-1 for m in count(1)) if isprime(p)) if n%3 else -1 # Chai Wah Wu, Jul 08 2024
CROSSREFS
KEYWORD
base,sign
AUTHOR
Toshitaka Suzuki, Jun 19 2024
STATUS
approved