Repdigit
A d-repdigit is a number composed of repetition of a single digit (in a given base, generally taken as base 10 unless otherwise specified). For example, the beast number 666 is a (base-10) repdigit. The following table gives the first few repdigits in bases b=2 to 10.
b OEIS b-repdigits
2 A000225 1,
3, 7, 15, 31, 63, 127, ...
3 A048328 1, 2, 4, 8, 13, 26,
40, 80, 121, ...
4 A048329 1, 2, 3, 5, 10, 15,
21, 42, 63, 85, 170, ...
5 A048330 1, 2, 3, 4, 6, 12,
18, 24, 31, 62, 93, 124, 156, ...
6 A048331 1,
2, 3, 4, 5, 7, 14, 21, 28, 35, 43, 86, 129, 172, ...
7 A048332 1,
2, 3, 4, 5, 6, 8, 16, 24, 32, 40, 48, 57, 114, 171, ...
8 A048333 1, 2, 3, 4, 5, 6, 7, 9, 18, 27, 36, 45, 54, 63, 73, 146, ...
9 A048334 1, 2, 3, 4, 5, 6, 7, 8, 10, 20, 30, 40, 50, 60, 70, 80, 91, 182, ...
10 A010785 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, ...
If the digits of a repdigit are all 1s, it is known as a repunit.
See also
Beast Number, Keith Number, RepunitExplore with Wolfram|Alpha
WolframAlpha
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References
Sloane, N. J. A. Sequences A000225, A010785, A048328, A048329, A048330, A048331, A048332, A048333, and A048334 in "The On-Line Encyclopedia of Integer Sequences."Referenced on Wolfram|Alpha
RepdigitCite this as:
Weisstein, Eric W. "Repdigit." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Repdigit.html