login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A190839 a(n) is the maximal prime divisor of 10^(2*n)+10^n+1. 0
37, 37, 333667, 9901, 2906161, 333667, 10838689, 99990001, 440334654777631, 2906161, 1344628210313298373, 999999000001, 900900900900990990990991, 10838689, 4185502830133110721, 9999999900000001, 13168164561429877, 440334654777631, 3931123022305129377976519, 39526741 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

(10^(2*n)+10^n+1)^3 is palindrome.

LINKS

Table of n, a(n) for n=1..20.

factordb, 10^(2*n)+10^n+1

FORMULA

a(n) = A006530(A066138(n)). - R. J. Mathar, Oct 30 2015

MATHEMATICA

f[n_]:=Max[Transpose[FactorInteger[10^(2n)+10^n+1]][[1]]]; Array[f, 20] (* Harvey P. Dale, Jun 10 2011 *)

PROG

(PARI) u(n)=10^(2*n)+10^n+1; for(n=1, 30, f=factor(u(n)); print1(f[matsize(f)[1], 1], ", ")) \\ Joerg Arndt, May 27 2011

CROSSREFS

Cf. A002780.

Sequence in context: A219450 A165858 A217544 * A185698 A043611 A296871

Adjacent sequences:  A190836 A190837 A190838 * A190840 A190841 A190842

KEYWORD

nonn,base

AUTHOR

Vladimir Shevelev, May 21 2011

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 4 17:55 EDT 2021. Contains 346455 sequences. (Running on oeis4.)