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A216479 a(n) is the least multiple of n which uses only the digit 1, or a(n) = -1 if no such multiple exists. 1
1, -1, 111, -1, -1, -1, 111111, -1, 111111111, -1, 11, -1, 111111, -1, -1, -1, 1111111111111111, -1, 111111111111111111, -1, 111111, -1, 1111111111111111111111, -1, -1, -1, 111111111111111111111111111, -1, 1111111111111111111111111111, -1, 111111111111111, -1, 111111, -1, -1, -1, 111, -1, 111111, -1, 11111, -1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) = -1 if and only if n is a multiple of 2 or 5. See comment in A216485. - Chai Wah Wu, Jun 21 2015

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..1000

CROSSREFS

Cf. A004290, A079339, A181060, A181061.

Sequence in context: A280142 A077573 A266435 * A123698 A123727 A282915

Adjacent sequences:  A216476 A216477 A216478 * A216480 A216481 A216482

KEYWORD

sign,base

AUTHOR

V. Raman, Sep 07 2012

STATUS

approved

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Last modified December 5 12:04 EST 2020. Contains 338947 sequences. (Running on oeis4.)