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A032684 Numbers k such that k surrounded by digit '7' is prime. 2

%I

%S 2,5,8,9,12,17,18,20,23,24,29,30,41,45,47,48,50,51,53,54,57,60,68,71,

%T 72,75,81,86,87,90,92,93,114,116,123,125,128,131,132,134,138,143,152,

%U 153,159,164,170,177,180,183,186,188,191,194,198,204,207

%N Numbers k such that k surrounded by digit '7' is prime.

%H Daniel Starodubtsev, <a href="/A032684/b032684.txt">Table of n, a(n) for n = 1..10000</a>

%o (Python)

%o from sympy import isprime

%o print([i for i in range(200) if isprime(int('7' + str(i) + '7'))]) # _Daniel Starodubtsev_, Apr 05 2020

%Y Cf. A032689.

%K nonn,base

%O 1,1

%A _Patrick De Geest_, May 15 1998

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Last modified April 15 07:40 EDT 2021. Contains 342975 sequences. (Running on oeis4.)