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
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..66
Programs
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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
Comments