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A103404 The 10^n-th palindromic prime. 1
2, 191, 94049, 114232411, 13649694631, 1565887885651, 175606737606571, 19508150605180591 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 24 14:46 EDT 2020. Contains 337321 sequences. (Running on oeis4.)