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A270026 a(n) is the smallest b for which the base-b representation of n contains at least one 0 (or 0 if no such base exists). 2
0, 2, 3, 2, 2, 2, 7, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For n > 1, a(n)=2 whenever n+1 is not a power of 2.

It is conjectured that the only terms that are neither 2 nor 3 in this sequence are a(7) and a(32767), which are 7 and 5 respectively.

a(n) > 0 for n >= 2 since the base-n representation of n is 10.

LINKS

Nathan Fox, Table of n, a(n) for n = 1..40000

Eric Weisstein's World of Mathematics, Ternary

MATHEMATICA

Table[SelectFirst[Range[2, 1200], DigitCount[n, #, 0] > 0 &], {n, 2, 120}] (* Michael De Vlieger, Mar 09 2016, Version 10 *)

PROG

(PARI) a(n) = if (n==1, 0, my(b=2); while(vecmin(digits(n, b)), b++); b); \\ Michel Marcus, Mar 09 2016

CROSSREFS

Cf. A117970, A216194.

Sequence in context: A306225 A077199 A145390 * A340703 A128049 A104543

Adjacent sequences:  A270023 A270024 A270025 * A270027 A270028 A270029

KEYWORD

nonn,base

AUTHOR

Nathan Fox, Mar 08 2016

STATUS

approved

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Last modified September 16 08:18 EDT 2021. Contains 347469 sequences. (Running on oeis4.)