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%I #16 Sep 05 2022 02:05:56
%S 1,5,7,8,16,20,25,31,32,34,37,41,43,46,53,58,59,61,62,64,67,73,79,80,
%T 82,83,85,86,92,94,101,103,106,112,115,118,119,122,125,133,139,151,
%U 154,157,158,164,166,172,179,187,188,196,197,200,206,208,214,217
%N Numbers k such that k surrounded by digit '3' is a prime.
%H Harvey P. Dale, <a href="/A032683/b032683.txt">Table of n, a(n) for n = 1..1000</a>
%t Select[Range[250],PrimeQ[FromDigits[Join[{3},IntegerDigits[#],{3}]]]&] (* _Harvey P. Dale_, Apr 18 2012 *)
%o (Python)
%o from sympy import isprime
%o def ok(n): return isprime(int('3' + str(n) + '3'))
%o print([k for k in range(220) if ok(k)]) # _Michael S. Branicky_, Sep 04 2022
%Y Cf. A032682, A032684, A032685, A032687.
%K nonn,base
%O 1,2
%A _Patrick De Geest_, May 15 1998
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