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A329792
Smallest positive k such that k*n contains only the digits 1,2,3,4,5, or -1 if no such k exists.
2
-1, 1, 1, 1, 1, 1, 2, 2, 3, 5, -1, 1, 1, 1, 1, 1, 2, 2, 3, 6, -1, 1, 1, 1, 1, 1, 2, 2, 4, 5, -1, 1, 1, 1, 1, 1, 4, 3, 3, 6, -1, 1, 1, 1, 1, 1, 7, 3, 3, 5, -1, 1, 1, 1, 1, 1, 2, 2, 4, 6, -1, 2, 2, 4, 8, 5, 2, 2, 8, 5, -1, 2, 2, 7, 3, 3, 2, 2, 3, 7, -1, 3, 16, 4, 3, 3, 4, 5, 4, 5, -1
OFFSET
0,7
COMMENTS
a(n) > 0 iff n is not a multiple of 10.
REFERENCES
G. Galperin and Y. J. Ionin (Proposers), and M. Reid (Solver), Problem 12034, Amer. Math. Monthly, 126:10, 950-951, Dec. 2019.
LINKS
PROG
(Python)
def A329792(n):
if n % 10:
m, s = 1, set('12345')
while not set(str(m*n)) <= s:
m += 1
return m
else:
return -1 # Chai Wah Wu, Dec 04 2019
CROSSREFS
Sequence in context: A093927 A067088 A065519 * A058256 A140183 A280408
KEYWORD
sign,look,base
AUTHOR
N. J. A. Sloane, Dec 03 2019
STATUS
approved