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 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

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Last modified November 29 06:17 EST 2023. Contains 367422 sequences. (Running on oeis4.)