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Primes congruent to 1 (mod 3) which only have the odd digits {1, 3, 7, 9}.
2

%I #16 Dec 01 2022 23:44:41

%S 7,13,19,31,37,73,79,97,139,193,199,313,331,337,373,379,397,733,739,

%T 919,937,991,997,1117,1171,1399,1777,1933,1993,1999,3313,3319,3331,

%U 3373,3391,3733,3739,3793,3919,3931,7177,7333,7393,7717,7933,7993,9133,9199,9319,9337,9391,9397,9733,9739,9931,9973

%N Primes congruent to 1 (mod 3) which only have the odd digits {1, 3, 7, 9}.

%C Potential candidates for A224929.

%C Subsequence of A002476. - _Michel Marcus_, May 06 2014

%H Harvey P. Dale, <a href="/A242190/b242190.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[ Prime@ Range@ 1250, Union@ Join[{1, 3, 7, 9}, IntegerDigits@#] == {1, 3, 7, 9} && Mod[#, 3] == 1 &]

%t Select[Flatten[Table[FromDigits/@Tuples[{1,3,7,9},n],{n,4}]],PrimeQ[#] && Mod[#,3]==1&] (* _Harvey P. Dale_, Jun 16 2017 *)

%Y Cf. A002476, A224929.

%K nonn,easy

%O 1,1

%A _Robert G. Wilson v_, May 06 2014