OFFSET
1,1
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..10000
EXAMPLE
13 is the first term, since 31 is also prime. 113 is a term, since 131 is prime. 101 is not allowed as a term: 011 is prime, but has a leading zero.
PROG
(Python)
from sympy import isprime
from itertools import combinations
def ok(n):
if not isprime(n): return False
s = list(str(n))
for i, j in combinations(range(len(s)), 2):
sij = s[:]
sij[i], sij[j] = sij[j], sij[i]
if sij[0] != "0" and sij != s and isprime(int("".join(sij))):
return True
return False
print([k for k in range(565) if ok(k)]) # Michael S. Branicky, Sep 07 2024
CROSSREFS
KEYWORD
base,nonn
AUTHOR
James S. DeArmon, Sep 06 2024
EXTENSIONS
Corrected and more terms from Michael S. Branicky, Sep 07 2024
STATUS
approved