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
KEYWORD
nonn,base
AUTHOR
André Engels, Mar 23 2016
STATUS
approved