A244927 Least positive number k such that k*n written in base 10 is either a repunit or of the form 1111....0000.

1, 5, 37, 25, 2, 185, 15873, 125, 12345679, 1, 1, 925, 8547, 79365, 74, 625, 65359477124183, 61728395, 5847953216374269, 5, 5291, 5, 48309178743961352657, 4625, 4, 42735, 4115226337448559670781893, 396825, 38314176245210727969348659, 37, 3584229390681, 3125, 3367, 326797385620915

Offset: 1

Author

Chai Wah Wu, Jul 08 2014

Keywords

• nonn
• base

Examples

			For n = 7, 15873*7 = 111111 and this is the least positive multiple of 7 that is either a repunit or of the form 1111...000.
		

Links

• M. F. Hasler, Table of n, a(n) for n = 1..1016 (first 100 terms from Chai Wah Wu), Mar 04 2025

Crossrefs

Cf. A244859, A079339, A004290. Equal to A079339 for the first 6 terms.

Formula

a(n) = A244859(n)/n.

a(3^k) = (10^(3^k)-1)/3^(k+2). a(n) <= (10^n-1)/(9*n). If n > 2 is not a power of 3, then a(n) <= (10^(n-1)-1)/(9*n). - Chai Wah Wu, Mar 04 2025