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%I #24 Apr 03 2023 10:36:12
%S 1,3,6,7,49,578,793,1322,1392,2392,3066,13479
%N Numbers n>0 such that (7*10^(n+2)+666)*10^n+7 is prime.
%C Or, indices of primes in A046720. Rudolf Ondrejka calls these "beastly palindromic primes".
%C Some of the larger entries may only correspond to probable primes.
%H Chris Caldwell, The Prime Glossary, <a href="https://t5k.org/glossary/xpage/BeastlyPrime.html">Beastly prime</a>
%H G. L. Honaker, Jr. and Chris Caldwell, <a href="https://t5k.org/curios/cpage/1032.html">Prime Curios! 76667</a>
%H R. Ondrejka, <a href="http://www.utm.edu/research/primes/lists/top_ten/">The Top Ten: a Catalogue of Primal Configurations</a>
%t Select[Range[10^3], PrimeQ[(7*10^(# + 2) + 666)*10^# + 7] &] (* _Arkadiusz Wesolowski_, Sep 08 2011 *)
%Y Cf. A046720, A186086.
%K nonn,base,more
%O 1,2
%A _Arkadiusz Wesolowski_, Feb 23 2011
%E a(12) added by _Arkadiusz Wesolowski_, Mar 16 2011
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