This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A103403 Palindromic primes q derived from palindromes p such that pi(p) = q. 5
 2, 2, 3, 3, 5, 11, 101, 151, 757, 797, 72727, 3485843, 7362637, 753535357, 32792329723 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS From a suggestion from Zak Seidov, Feb 02 2005. a(16) > pi(32*10^12). [From Donovan Johnson, Dec 03 2009] LINKS 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. Sequence in context: A055501 A096010 A102330 * A052473 A165122 A051715 Adjacent sequences:  A103400 A103401 A103402 * A103404 A103405 A103406 KEYWORD base,nonn AUTHOR Robert G. Wilson v, Feb 03 2005 EXTENSIONS a(15) from Donovan Johnson, Dec 03 2009 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .