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 A077189 #11 Mar 04 2020 20:28:39 %S A077189 1,12321,0,12345654321,12321,121,12345654321,0 %N A077189 Smallest concatenation 123...(k-1) k (k-1)...321 (a concatenation of natural numbers from 1 to k and back to 1) that is a multiple of 2n-1, or 0 if no such number exists. %C A077189 a(5k+3) = 0. Are there any other values of n such that a(n) = 0? %C A077189 The next value, 2n-1 = 17, has k = 109, for a total of 435 digits and is too large to include. - _Franklin T. Adams-Watters_, Jun 02 2006 %H A077189 Jinyuan Wang, <a href="/A077189/b077189.txt">Table of n, a(n) for n = 1..11</a> %e A077189 a(5) = 12321 is a multiple of 9. %Y A077189 Cf. A077180, A077181, A077182, A077183, A077184, A077186, A077188, A077190. %Y A077189 Cf. A120008. %K A077189 nonn,base %O A077189 1,2 %A A077189 _Amarnath Murthy_, Nov 01 2002 %E A077189 More terms from _Franklin T. Adams-Watters_, Jun 02 2006