A270832 - OEIS

A270832

Number of bases in which n is written using more than 1 digit, all of which are distinct.

0, 1, 1, 1, 2, 3, 4, 4, 5, 5, 8, 7, 9, 9, 11, 10, 12, 12, 16, 14, 16, 16, 18, 17, 19, 19, 22, 22, 24, 23, 25, 24, 27, 27, 30, 27, 30, 32, 34, 32, 35, 34, 36, 37, 38, 38, 41, 39, 42, 41, 45, 45, 48, 47, 48, 48, 49, 51, 53, 48, 53, 54, 55, 53, 57, 58, 60, 60, 63, 62

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OFFSET

1,5

COMMENTS

n/2 - 1 <= a(n) < n.

a(n) is not always <= n - sqrt(n) + 1. Counterexample: for n = 1000000, a(n) = 999911 > 999001 = n - sqrt(n) + 1. - Lucas O. Wagner, Jul 27 2019

LINKS

Jinyuan Wang, Table of n, a(n) for n = 1..10000

EXAMPLE

a(5) = 2 because 5 equals 10 in base 5, 12 in base 3. In base 2 (101) and base 4 (11) there are repeated digits, in base > 5 it is only one digit long.

MATHEMATICA

Table[Count[Function[b, AllTrue[DigitCount[n, b], # <= 1 &]] /@ Range[2, n], True], {n, 70}] (* Michael De Vlieger, Mar 24 2016, Version 10 *)

PROG

(PARI) a(n) = sum(b=2, n, v = digits(n, b); (#v > 1) && (#v == #Set(v))); \\ Michel Marcus, Mar 24 2016

CROSSREFS

Sequence in context: A110532 A049987 A343397 * A257646 A051898 A092032

Adjacent sequences: A270829 A270830 A270831 * A270833 A270834 A270835

KEYWORD

nonn,base

AUTHOR

André Engels, Mar 23 2016

STATUS

approved