A059972 - OEIS

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A059972

a(n) is the least positive integer k such that all digits of k are 0 or 1 in exactly n different bases B, where 2 <= B <= k; i.e., such that A068953(k)=n.

2, 3, 4, 9, 30, 81, 4096, 531441, 16777216

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OFFSET

1,1

COMMENTS

Is every term except 30 a power of either 2 or 3?

LINKS

Table of n, a(n) for n=1..9.

EXAMPLE

For n=4: 9 written in bases 2 through 9 is 1001, 100, 21, 14, 13, 12, 11, 10. In 4 bases, namely 2, 3, 8 and 9, all digits are 0 or 1.

MATHEMATICA

f[1]=0; f[k_] := Length[Select[Rest[Union[Divisors[k], Divisors[k-1]]], Max@@IntegerDigits[k, # ]==1&]]; a[n_] := For[k=1, True, k++, If[f[k]==n, Return[k]]]

CROSSREFS

Cf. A068953.

Sequence in context: A014118 A007704 A328836 * A245930 A086432 A186928

Adjacent sequences: A059969 A059970 A059971 * A059973 A059974 A059975

KEYWORD

more,base,nonn

AUTHOR

Naohiro Nomoto, Mar 28 2002

EXTENSIONS

Edited by Dean Hickerson, Mar 31 2002

STATUS

approved