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Numbers that are repdigits with length > 2 in more than two bases.
10

%I #20 Jul 10 2019 03:02:38

%S 4095,32767,65535,67053,262143,265720,531440,1048575,2097151,4381419,

%T 5592405,7174453,9808617,11184810,13938267,14348906,16777215,19617234,

%U 21523360,29425851,39234468,43046720,48686547,49043085,58851702,61035156,68660319,71270178

%N Numbers that are repdigits with length > 2 in more than two bases.

%C Most of the terms of A167783 are repdigits with length > 2 in only two bases.

%C For any b > 1 and k > 2, b^(4*k)-1 is a repdigit with length > 2 in bases b, b^2 and b^4; hence this sequence is infinite. - _Rémy Sigrist_, Aug 19 2017

%H Rémy Sigrist, <a href="/A290869/b290869.txt">Table of n, a(n) for n = 1..777</a>

%H Rémy Sigrist, <a href="/A290869/a290869.txt">C# program for A290869</a>

%H Rémy Sigrist, <a href="/A290869/a290869_1.txt">C++ program for A290869</a>

%e 67053 is a repdigit with more than 2 digits in three bases: [31,31,31]_46, [21,21,21]_56, [3,3,3]_149.

%o (PARI) isok(n)=my(nb = 0); for (b=2, n-1, d = digits(n, b); if ((#d > 2) && (#Set(d) == 1), nb++); if (nb > 2, return (1)); ); return (0);

%o (C#) See Links section.

%o (C++) See Links section.

%Y Subsequence of A167783.

%K nonn,base

%O 1,1

%A _Michel Marcus_, Aug 13 2017

%E More terms from _Giovanni Resta_, Aug 13 2017