A210546 Emirps whose products of digits are prime.

13, 17, 31, 71, 113, 311, 1151, 1511, 111211, 112111, 1111711, 1171111, 11111117, 11113111, 11131111, 71111111, 111111131, 131111111, 1111115111, 1115111111, 11111111113, 31111111111, 111111111111111131, 131111111111111111, 1111111111111111111111111511

Offset: 1

Author

Lekraj Beedassy, Mar 22 2012

Keywords

• nonn
• base

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..66

Crossrefs

Cf. A006567, A046703, A210547, A210548.

Programs

Python

from _future_ import division
from sympy import isprime
A210546_list = []
for l in range(1,20):
    q = (10**l-1)//9
    for i in range(l):
        for p in [2,3,5,7]:
            r = q+(p-1)*10**i
            s, t = str(r), str(r)[::-1]
            if s != t and isprime(r) and isprime(int(t)):
                A210546_list.append(r) # Chai Wah Wu, Aug 15 2017

Extensions

5 more terms from Alois P. Heinz, Mar 29 2012