A077360 Primes whose external digits as well as internal digits form a prime.

127, 131, 137, 139, 151, 157, 173, 179, 223, 229, 233, 239, 331, 337, 421, 431, 433, 457, 523, 631, 677, 733, 739, 751, 773, 823, 829, 839, 853, 859, 937, 977, 1021, 1031, 1033, 1039, 1051, 1117, 1171, 1193, 1231, 1237, 1291, 1297, 1319, 1373, 1433, 1439

Offset: 1

Author

Amarnath Murthy, Nov 05 2002

Keywords

• base
• nonn
• easy

Comments

Intersection of A069686 and A077359.

Examples

			139 is a term as 19 and 3 are both primes.
		

Links

• Jason Yuen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A069686, A077359.

Programs

PARI

forprime(p=1,1440,if(isprime(indigs(p))&&isprime(exdigs(p)),print1(p,",")))

Python

from sympy import isprime, primerange
for p in primerange(100, 1440):
    if isprime(int(str(p)[1:-1])) and isprime(int(str(p)[0]+str(p)[-1])):
        print(p)  # Jason Yuen, Apr 21 2024

Extensions

Edited and extended by Klaus Brockhaus, Nov 06 2002