This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A317173 #9 Jul 28 2018 11:13:29 %S A317173 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 A317173 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 A317173 2,2,1,2,2,2,2,2,2,2,2,2,1,2,2,2,2,2,2 %N A317173 a(n) is the least k > 0 such that k * n contains a digit 1 in its decimal representation. %F A317173 1 <= a(n) <= 5. %F A317173 a(n) <= A190302(n). %F A317173 a(n) = A317175(n, 1). %F A317173 a(10 * n) = a(n). %e A317173 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 A317173 (PARI) a(n) = for (k=1, oo, if (setsearch(Set(digits(k*n)), 1), return (k))) %Y A317173 Cf. A011531, A190302, A317175. %K A317173 nonn,base,easy %O A317173 1,2 %A A317173 _Rémy Sigrist_, Jul 23 2018