OFFSET
1,2
COMMENTS
Previous name: Indices of primes appearing in A046941.
LINKS
Eric Weisstein's World of Mathematics, Palindromic Prime.
MATHEMATICA
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]]]] ]]]];
p = 0; Do[p = NextPalindrome[p]; While[ !PrimeQ[p], p = NextPalindrome[ p]]; q = IntegerDigits[ PrimePi[ p]]; If[Reverse[q] == q, Print[{p, FromDigits[q]}]], {n, 10^4}] (* Robert G. Wilson v, Feb 03 2005 *)
ParallelDo[If [PalindromeQ @ i && PalindromeQ @ Prime @i, Print @i], {i, 6*10^8}] (* Mikk Heidemaa, May 24 2024 *)
CROSSREFS
KEYWORD
nice,nonn,base,more
AUTHOR
EXTENSIONS
a(7) from Giovanni Resta, May 14 2003
New name and offset by Ivan Neretin, Jun 02 2016
a(8) from Giovanni Resta, Aug 10 2019
STATUS
approved