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A167782
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Numbers that are repdigits with length > 2 in some base.
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15
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0, 7, 13, 15, 21, 26, 31, 40, 42, 43, 57, 62, 63, 73, 80, 85, 86, 91, 93, 111, 114, 121, 124, 127, 129, 133, 146, 156, 157, 170, 171, 172, 182, 183, 211, 215, 219, 222, 228, 241, 242, 255, 259, 266, 273, 285, 292, 307, 312, 314, 333, 341, 342, 343, 364, 365, 366
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OFFSET
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1,2
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COMMENTS
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Definition requires "length > 2" because all numbers n > 2 are trivially represented as "11" in base n-1.
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LINKS
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EXAMPLE
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26 is a term because 26_10 = 222_3.
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PROG
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(PARI) digits(n, b) = if(n<b, [n], concat(digits(floor(n/b), b), n%b))
is_repdigit(d) = {local(a, r); r=1; a=d[1]; for(i=2, matsize(d)[2], if(a!=d[i], r=0)); r}
for(n=1, 1200, b=2; while(n>=b^2+b+1, d=digits(n, b); if(is_repdigit(d), print(n, " = ", d, " base ", b)); b++)) \\ Michael B. Porter
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CROSSREFS
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Cf. A167783 (Numbers that are repdigits with length > 2 in more than one base).
Cf. A053696 (Numbers which are repunits in some base).
Cf. A158235 (Numbers n whose square can be represented as a repdigit number in some base < n).
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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