A381530 a(n) is the least k > 0 such that n / k contains a digit 1 in its decimal representation.

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

Offset: 1

Author

Ctibor O. Zizka, Feb 26 2025

Keywords

• nonn
• base

Examples

			n = 7:
7/1 = 7
7/2 = 3.5
7/3 = 2.33...
7/4 = 1.75 contains a digit 1, thus a(7) = 4.
		

Crossrefs

Cf. A317173, A371706.

Programs

Mathematica

a[n_] := Module[{k = 1}, While[FreeQ[RealDigits[n/k][[1]], 1], k++]; k]; Array[a, 100] (* Amiram Eldar, Feb 26 2025 *)