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a(n) is the least k > 0 such that k * n contains a digit 1 in its decimal representation.
3

%I #9 Jul 28 2018 11:13:29

%S 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,

%T 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,

%U 2,2,1,2,2,2,2,2,2,2,2,2,1,2,2,2,2,2,2

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

%F 1 <= a(n) <= 5.

%F a(n) <= A190302(n).

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

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

%e 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.

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

%Y Cf. A011531, A190302, A317175.

%K nonn,base,easy

%O 1,2

%A _Rémy Sigrist_, Jul 23 2018