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%I #11 Oct 14 2019 07:30:48
%S 1,3,9,19,27,33,39,57,87,97,159,177,187,433,487,541,603,691,717,753,
%T 757,853,949,1257,1471,1707,2277,2367,2617,2953,4317,4507,4623,4779,
%U 4797,5773,6481,6757,6777,7017,7351,7417,7471,7479,7747,7797,7813,7977
%N Prefixing, suffixing or inserting a 7 in the number anywhere gives a prime.
%H Giovanni Resta, <a href="/A069832/b069832.txt">Table of n, a(n) for n = 1..2399</a> (terms < 10^13, first 201 terms from Harvey P. Dale)
%t psi7Q[n_]:=Module[{idn=IntegerDigits[n]},And@@PrimeQ[FromDigits/@ Table[ Insert[ idn,7,i],{i,Length[idn]+1}]]]; Select[Range[8000],psi7Q] (* _Harvey P. Dale_, Sep 18 2012 *)
%Y Cf. A068674, A068679, A069833.
%K base,nonn
%O 1,2
%A _Amarnath Murthy_, Apr 14 2002
%E More terms from _Vladeta Jovovic_, Apr 16 2002
%E Offset changed to 1 by _Giovanni Resta_, Oct 14 2019
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