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%I #6 Aug 25 2012 09:44:44
%S 2,191,94049,114232411,13649694631,1565887885651,175606737606571,
%T 19508150605180591
%N The 10^n-th palindromic prime.
%e 2, 3, 5, 7, 11, 101, 131, 151, 181 and 191 are the first ten palindromic primes.
%t NextPalindrome[n_] := Block[ {l = Floor[ Log[10, n] + 1], idn = IntegerDigits[n]}, If[ Union[ idn] == {9}, Return[n + 2], If[l < 2, Return[n + 1], If[ FromDigits[ Reverse[ Take[ idn, Ceiling[l/2]]]] FromDigits[ Take[ idn, -Ceiling[l/2]]], FromDigits[ Join[ Take[ idn, Ceiling[l/2]], Reverse[ Take[ idn, Floor[l/2]]] ]], idfhn = FromDigits[ Take[ idn, Ceiling[l/2]]] + 1; idp = FromDigits[ Join[ IntegerDigits[ idfhn], Drop[ Reverse[ IntegerDigits[ idfhn]], Mod[l, 2]]]] ]]]];
%t pal = 0; Do[pal = NextPalindrome[pal]; Do[While[pal = NextPalindrome[pal]; ! PrimeQ[pal], ], {i, 10^(n - 1) + 1, 10^n}]; Print[pal], {n, 0, 8}]
%Y Cf. A083816.
%K base,nonn
%O 0,1
%A _Robert G. Wilson v_, Feb 03 2005
%E a(7) from _Donovan Johnson_, Aug 25 2012
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