A059694 - OEIS

%I #20 Feb 23 2023 07:27:29

%S 53,2477,4547,5009,7499,8831,9839,11027,24821,26393,29921,36833,46073,

%T 46769,47711,49307,53069,59621,64283,66041,79901,84017,93263,115679,

%U 133103,151121,169523,197651,207017,236807,239231,255191,259949,265271,270071,300431,330047

%N Primes p such that 1p1, 3p3, 7p7 and 9p9 are all primes.

%C All terms == 1 (mod 6). The sequence is apparently infinite. There are 16486 terms up to 10^9. - _Zak Seidov_, Jan 17 2014

%C Intersection of A069687, A069688, A069689, and A069690. - _Zak Seidov_, Jan 17 2014

%H Zak Seidov, <a href="/A059694/b059694.txt">Table of n, a(n) for n = 1..10000</a>

%e 53 is a term because 1531, 3533, 7537 and 9539 are primes.

%o (Python)

%o from sympy import isprime, nextprime

%o from itertools import islice

%o def agen(): # generator of terms

%o     p = 2

%o     while True:

%o         sp = str(p)

%o         if all(isprime(int(d+sp+d)) for d in "1379"):

%o             yield p

%o         p = nextprime(p)

%o print(list(islice(agen(), 40))) # _Michael S. Branicky_, Feb 23 2023

%Y Cf. A059677, A032682, A059693.

%K nonn,base

%O 1,1

%A _Patrick De Geest_, Feb 07 2001