A124232 Numbers n such that prime(n) and pi(n) are palindromic.

1, 2, 3, 4, 5, 26, 32, 36, 138, 3691, 6987, 7193, 86969, 117766, 127150, 142583, 515786, 531448, 539596, 615980, 646060, 17262354, 39816443, 47548105, 48803361, 49426747, 528977302, 538348374, 1475057753, 1559827952, 2994135736, 60040412496, 64516992534, 333771325433, 11655934712628, 21872729899659, 22903935103276, 28311805106395, 29606335619415

Offset

1,2

Links

Table of n, a(n) for n=1..39.

Mathematica

NextPalindrome[n_] := Block[{lg = Floor@ Log[10, n] + 1, idn = IntegerDigits@n}, If[Union@ idn == {9}, Return[n + 2], If[lg < 2, Return[n + 1], If[ FromDigits@ Reverse@ Take[idn, Ceiling[lg/2]] > FromDigits@ Take[idn, -Ceiling[lg/2]], FromDigits@ Join[ Take[idn, Ceiling[lg/2]], Reverse@ Take[idn, Floor[lg/2]]], idfhn = FromDigits@ Take[idn, Ceiling[lg/2]] + 1; idp = FromDigits@ Join[IntegerDigits@ idfhn, Drop[ Reverse@ IntegerDigits@ idfhn, Mod[lg, 2]]] ]]]];
palQ[n_Integer] := Module[{idn = IntegerDigits@n}, idn == Reverse@ idn]; lst = {}; k = 1; While[k < 10^12, If[ PrimeQ@k && palQ@PrimePi@PrimePi@k, Print@PrimePi@k; AppendTo[lst, PrimePi@k]]; k = NextPalindrome@k]; lst (* Robert G. Wilson v *)

Crossrefs

Subsequence of A075807 = numbers n such that n-th prime is palindromic.

Sequence in context: A088865 A237342 A075807 * A051143 A084853 A115337

Adjacent sequences: A124229 A124230 A124231 * A124233 A124234 A124235

Keyword

base,nonn

Author

Tanya Khovanova, Dec 13 2006

Extensions

a(22) - a(31) from Robert G. Wilson v, Dec 14 2006

a(32)-a(33) from Donovan Johnson, Jul 19 2012

a(34) from Chai Wah Wu, Sep 12 2019

a(35)-a(39) from Chai Wah Wu, Sep 19 2019

Status

approved