A317173 a(n) is the least k > 0 such that k * n contains a digit 1 in its decimal representation.

1, 5, 4, 3, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 1, 5, 5, 5, 4, 4, 3, 4, 4, 4, 1, 4, 4, 3, 3, 3, 3, 3, 3, 3, 1, 3, 3, 3, 3, 3, 3, 3, 3, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

1 <= a(n) <= 5.

a(n) <= A190302(n).

a(n) = A317175(n, 1).

a(10 * n) = a(n).

Example

The multiples of 3 are: 3, 6, 9, 12, 15, etc.; 12 is the first one containing the digit 1, hence a(3) = 12/3 = 4.

Mathematica

Table[Module[{k=1}, While[DigitCount[k*n, 10, 1]==0, k++]; k], {n, 90}] (* Harvey P. Dale, May 25 2026 *)

Prog

(PARI) a(n) = for (k=1, oo, if (setsearch(Set(digits(k*n)), 1), return (k)))

Crossrefs

Cf. A011531, A190302, A317175.

Sequence in context: A266084 A055116 A276373 * A190302 A223475 A190137

Adjacent sequences: A317170 A317171 A317172 * A317174 A317175 A317176

Keyword

nonn,base,easy

Author

Rémy Sigrist, Jul 23 2018

Status

approved