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 A284750 #43 Jun 26 2017 07:58:22 %S A284750 1,1,1,2,5,1,1,1,1,3,3,2,2,9,2,2,9,7,8,6,6,33,256,1,1,1,1,26,5,1,1,1, %T A284750 1,149,24,4,159,4,130,3,3,3,3,118,16,128,16,3,3,3,3,14,16,16,840,13, %U A284750 89,15,88,2,2,12,2,2,78,11,13,76,597,12,71,2,2,555,2 %N A284750 a(n) = least k > 0 such that k * n in factorial base representation contains only 0's and 1's. %C A284750 a(n) = 1 iff n belongs to A059590. %C A284750 a(a(n)) <= n for any n > 0. %H A284750 Rémy Sigrist, <a href="/A284750/b284750.txt">Table of n, a(n) for n = 1..2000</a> %H A284750 Wikipedia, <a href="https://en.wikipedia.org/wiki/Factorial_number_system">Factorial number system</a> %H A284750 <a href="/index/Fa#facbase">Index entries for sequences related to factorial base representation</a> %F A284750 a(n) = A286820(n) / n. %e A284750 The first terms, alongside n*a(n) in decimal and factorial base, are: %e A284750 n a(n) n*a(n) n*a(n) in factorial base %e A284750 -- ---- ------ ------------------------ %e A284750 1 1 1 1 %e A284750 2 1 2 1,0 %e A284750 3 1 3 1,1 %e A284750 4 2 8 1,1,0 %e A284750 5 5 25 1,0,0,1 %e A284750 6 1 6 1,0,0 %e A284750 7 1 7 1,0,1 %e A284750 8 1 8 1,1,0 %e A284750 9 1 9 1,1,1 %e A284750 10 3 30 1,1,0,0 %e A284750 11 3 33 1,1,1,1 %e A284750 12 2 24 1,0,0,0 %e A284750 13 2 26 1,0,1,0 %e A284750 14 9 126 1,0,1,0,0 %e A284750 15 2 30 1,1,0,0 %e A284750 16 2 32 1,1,1,0 %e A284750 17 9 153 1,1,1,1,1 %e A284750 18 7 126 1,0,1,0,0 %e A284750 19 8 152 1,1,1,1,0 %e A284750 20 6 120 1,0,0,0,0 %o A284750 (PARI) isA059590(n) = my (r=2); while (n, if (n%r > 1, return (0), n\=r; r++)); return (1) %o A284750 a(n) = for (k=1, oo, if (isA059590(k*n), return (k))) %Y A284750 Cf. A059590, A286820. %K A284750 nonn,base %O A284750 1,4 %A A284750 _Rémy Sigrist_, Jun 25 2017