A103404 The 10^n-th palindromic prime.

2, 191, 94049, 114232411, 13649694631, 1565887885651, 175606737606571, 19508150605180591

Offset

0,1

Links

Table of n, a(n) for n=0..7.

Example

2, 3, 5, 7, 11, 101, 131, 151, 181 and 191 are the first ten palindromic primes.

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]]]] ]]]];
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}]

Crossrefs

Cf. A083816.

Sequence in context: A085937 A142890 A201183 * A232822 A230228 A197249

Adjacent sequences: A103401 A103402 A103403 * A103405 A103406 A103407

Keyword

base,nonn

Author

Robert G. Wilson v, Feb 03 2005

Extensions

a(7) from Donovan Johnson, Aug 25 2012

Status

approved