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 A070529 #26 May 04 2022 14:20:21 %S A070529 1,2,4,4,4,32,4,16,12,16,4,128,8,16,64,64,4,384,2,128,128,96,2,1024, %T A070529 32,64,64,256,32,8192,8,2048,64,64,128,3072,8,8,64,2048,16,24576,16, %U A070529 1536,768,64,4,8192,16,1024,256,512,16,8192,256,4096 %N A070529 Number of divisors of repunit 111...111 (with n digits). %H A070529 <a href="/A070529/b070529.txt">Table of n, a(n) for n = 1..352</a> %F A070529 a(n) = A000005(A002275(n)). %F A070529 a(n) = A070528(n)*A051064(n)/(A051064(n)+2). %F A070529 a(A004023(n)) = 2. - _Michel Marcus_, Sep 09 2015 %F A070529 a(A046413(n)) = 4. - _Bruno Berselli_, Sep 09 2015 %e A070529 a(9) = 12 since the divisors of 111111111 are 1, 3, 9, 37, 111, 333, 333667, 1001001, 3003003, 12345679, 37037037, 111111111. %o A070529 (PARI) a(n) = numdiv(10^n\9); \\ _Michel Marcus_, Sep 09 2015 %Y A070529 Cf. A000005, A002275, A070528, A051064, A004023, A046413, A003020, A095370, A176973, A046053, A046412, A102380. %K A070529 base,nonn %O A070529 1,2 %A A070529 _Henry Bottomley_, May 02 2002 %E A070529 Terms to a(280) in b-file from _Hans Havermann_, Aug 20 2011 %E A070529 a(281)-a(322) in b-file from _Ray Chandler_, Apr 22 2017 %E A070529 a(323)-a(352) ib b-file from _Max Alekseyev_, May 04 2022