Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A103403
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A103403 Palindromic primes q derived from palindromes p such that pi(p) = q. +0
6
2, 2, 3, 3, 5, 11, 101, 151, 757, 797, 72727, 3485843, 7362637, 753535357 (list; graph; listen)
OFFSET

1,1

COMMENT

From a suggestion from Zak Seidov (zakseidov(AT)yahoo.com), Feb 02 2005.

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; a = {}; Do[p = NextPalindrome[p]; q = PrimePi[p]; If[PrimeQ[q], r = IntegerDigits[q]; If[Reverse[r] == r, Print[{p, q}]; AppendTo[a, q]]], {n, 10^6}]; a

CROSSREFS

Cf. A046941, A046942, A103357, A103358, A103402.

Adjacent sequences: A103400 A103401 A103402 this_sequence A103404 A103405 A103406

Sequence in context: A055501 A096010 A102330 this_sequence A052473 A051715 A143269

KEYWORD

base,nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 03 2005

page 1

Search completed in 0.002 seconds

Lookup | Welcome | Find friends | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
More pages | Superseeker | Maintained by N. J. A. Sloane (njas@research.att.com)

Last modified October 11 13:47 EDT 2008. Contains 144830 sequences.


AT&T Labs Research