login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A103357 Numbers n such that n and pi(n) (A000720) are palindromic. 5
1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 262, 323, 393, 525, 535, 555, 666, 818, 878, 949, 2002, 3773, 5775, 6116, 13031, 19591, 39093, 41414, 47374, 59295, 63236, 81918, 94549, 95759, 252252, 394493, 594495, 662266, 674476, 686686, 698896, 764467 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..44.

FORMULA

a(n) = P_A103358(n).

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 = IntegerDigits[ PrimePi[ p]]; If[ Reverse[q] == q, Print[{p, FromDigits[q]}]; AppendTo[a, p]], {n, 10^4}]; a (* Robert G. Wilson v, Feb 03 2005 *)

CROSSREFS

Corresponding palindromic pi(n) in A103358.

Cf. A046941, A046942, A103358, A103402, A103403.

Sequence in context: A250412 A201060 A201064 * A055931 A250411 A250410

Adjacent sequences:  A103354 A103355 A103356 * A103358 A103359 A103360

KEYWORD

easy,base,nonn

AUTHOR

Zak Seidov, Feb 02 2005

EXTENSIONS

More terms from Robert G. Wilson v, Feb 03 2005

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 19 14:52 EST 2018. Contains 317352 sequences. (Running on oeis4.)