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A131646
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Numbers that can be written from base 2 to base 18 using only the digits 0 to 9 (conjectured to be complete).
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5
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 18, 19, 20, 1027, 1028, 1029, 14745, 9020076688681, 9439828025162228377, 9439829801208141318
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OFFSET
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1,3
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COMMENTS
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Originally checked to 2^20356 (or 5.8*10^6127) in Nov 2008.
It appears that 19 and 20 are the only numbers > 9 that can be written up to base 19 only using digits 0 to 9 and 20 is the only number > 9 that can be written up to base 20 only using digits 0 to 9.
It is a plausible conjecture that there are no more terms, but this has not been proved. - N. J. A. Sloane, Nov 17 2017
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REFERENCES
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B. R. Barwell, Numbers Without Letters, Journal of Recreational Mathematics, Vol. 25:3 (1993), 174-179.
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LINKS
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MATHEMATICA
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f[n_] := Total[Total@ Drop[RotateRight[DigitCount[n, #]], 10] & /@ Range[11, 18]]; Select[Range[0, 20000], f@ # == 0 &] (* Michael De Vlieger, Aug 29 2015 *)
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PROG
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(PARI) isok(n) = if (n, for (b=11, 18, if (vecmax(digits(n, b))>9, return(0)))); 1; \\ Michel Marcus, Aug 30 2015
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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