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Palindromic primes that yield a prime when sandwiched between two 7's. (Prefixing and suffixing a 'seven' on both sides yields another pal prime).
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%I #10 Dec 19 2024 17:39:16

%S 2,5,131,191,797,11411,15551,30203,31013,32423,36263,36563,38183,

%T 39293,72227,74747,77477,94349,94949,1003001,1055501,1074701,1085801,

%U 1120211,1123211,1153511,1178711,1183811,1221221,1311131,1317131,1363631

%N Palindromic primes that yield a prime when sandwiched between two 7's. (Prefixing and suffixing a 'seven' on both sides yields another pal prime).

%H Harvey P. Dale, <a href="/A088271/b088271.txt">Table of n, a(n) for n = 1..100</a>

%e 191 is a member as 71917 is also a prime.

%t Select[Prime[Range[110000]],PalindromeQ[#]&&PrimeQ[FromDigits[Join[{7},IntegerDigits[#],{7}]]]&] (* _Harvey P. Dale_, Dec 19 2024 *)

%Y Cf. A088269, A088270, A088272.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Sep 28 2003

%E More terms from _David Wasserman_, Jul 28 2005