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A306424 Numbers n such that the base-b expansion of n for each b = 3..n-1 never contains more than two distinct digits. 0
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 16, 17, 20, 22, 23, 25, 26, 31, 37, 43 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Conjecture: The sequence is finite, with 43 being the last term.

I checked the conjecture to 10809638.

LINKS

Table of n, a(n) for n=1..23.

EXAMPLE

10 is a term of the sequence, since the base-b expansions of 10 for b = 3..9 are 101, 22, 20, 14, 13, 12, 11, respectively, and none of those expansions contain more than two distinct digits.

MATHEMATICA

Select[Range@ 100, Max@ Table[Length@ Union@ IntegerDigits[#, b], {b, 3, # - 1}] <= 2 &] (* Michael De Vlieger, Feb 15 2019 *)

PROG

(PARI) is(n) = for(b=3, n-1, my(d=digits(n, b)); if(#vecsort(d, , 8) > 2, return(0))); 1

CROSSREFS

Sequence in context: A154314 A239348 A191881 * A005524 A191890 A247814

Adjacent sequences:  A306421 A306422 A306423 * A306425 A306426 A306427

KEYWORD

nonn,base,more

AUTHOR

Felix Fröhlich, Feb 14 2019

STATUS

approved

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Last modified September 29 18:27 EDT 2020. Contains 337432 sequences. (Running on oeis4.)