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%I #14 Sep 05 2022 02:05:42
%S 1,2,10,19,20,23,31,34,41,43,47,53,61,62,64,67,68,71,73,74,76,82,83,
%T 85,92,94,100,101,107,109,112,113,115,119,122,124,130,136,145,149,152,
%U 163,190,193,196,200,211,217,218,221,226,236,239,241,245
%N Numbers k such that k surrounded by digit '9' is a prime.
%H Harvey P. Dale, <a href="/A032685/b032685.txt">Table of n, a(n) for n = 1..1000</a>
%t Select[Range[300],PrimeQ[FromDigits[Join[{9},IntegerDigits[#],{9}]]]&] (* _Harvey P. Dale_, Jul 20 2012 *)
%o (Python)
%o from sympy import isprime
%o def ok(n): return isprime(int('9' + str(n) + '9'))
%o print([k for k in range(250) if ok(k)]) # _Michael S. Branicky_, Sep 04 2022
%Y Cf. A032682, A032683, A032684, A032690.
%K nonn,base
%O 1,2
%A _Patrick De Geest_, May 15 1998
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