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%I #17 Jul 12 2020 14:37:47
%S 3,131,32397985356295141314159265358979323
%N Palindromic primes formed from decimal expansion of Pi written backwards then forwards.
%C The next term 729096599629...1413141...926995690927 has 2971 digits. - _Metin Sariyar_, Jul 07 2020
%H Chris K. Caldwell and G. L. Honaker, Jr., <a href="https://primes.utm.edu/curios/page.php?number_id=21081">Prime Curios! 729...927 (2971-digits)</a>
%t l={};Do[a=Floor[Pi*10^n];r=IntegerReverse[a];r2=Floor[r/10];c=FromDigits[Flatten[IntegerDigits/@Join[r2,a]]];
%t If[PrimeQ[c],AppendTo[l, c]],{n,0,100}];l (* _Metin Sariyar_, Jul 07 2020 *)
%Y Cf. A000796, A007523, A039954.
%K base,nonn,bref
%O 1,1
%A _G. L. Honaker, Jr._