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Palindromic prime numbers == 1 (mod 9).
1

%I #14 May 15 2021 18:26:11

%S 181,757,919,12421,16561,18181,19891,30403,34543,35353,70507,71317,

%T 77977,78787,95959,96769,97579,98389,1008001,1065601,1114111,1163611,

%U 1196911,1212121,1245421,1253521,1278721,1286821,1327231,1335331,1343431,1409041,1490941

%N Palindromic prime numbers == 1 (mod 9).

%H Shyam Sunder Gupta, <a href="/A229877/b229877.txt">Table of n, a(n) for n = 1..1005</a>

%t t = {}; Do[z = n*10^(IntegerLength[n] - 1) + FromDigits@Rest@Reverse@IntegerDigits[n]; If[PrimeQ[z] && Mod[z, 9] == 1, AppendTo[t, z]], {n, 1, 99999}]; t

%t Select[Prime[Range[115000]],PalindromeQ[#]&&Mod[#,9]==1&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 15 2021 *)

%Y Cf. A002385, A229875.

%K nonn,base,less

%O 1,1

%A _Shyam Sunder Gupta_, Oct 02 2013