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A190839
a(n) is the greatest prime divisor of 10^(2*n)+10^n+1.
1
37, 37, 333667, 9901, 2906161, 333667, 10838689, 99990001, 440334654777631, 2906161, 1344628210313298373, 999999000001, 900900900900990990990991, 10838689, 4185502830133110721, 9999999900000001, 13168164561429877, 440334654777631, 3931123022305129377976519, 39526741
OFFSET
1,1
COMMENTS
(10^(2*n)+10^n+1)^3 is palindrome.
LINKS
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
KEYWORD
nonn,base,changed
AUTHOR
Vladimir Shevelev, May 21 2011
STATUS
approved