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 A387422 #10 Sep 02 2025 01:41:57
%S A387422 1,1,1,1,1,3,1,1,1,2,1,2,2,2,2,1,3,4,2,4,2,2,1,2,2,1,1,5,3,1,1,1,1,1,
%T A387422 1,2,4,1,1,3,4,1,3,3,2,2,1,2,2,1,1,3,4,2,1,3,1,1,3,1,4,2,2,1,2,3,4,1,
%U A387422 1,3,3,1,5,1,1,3,1,2,2,3,1,1,4,1,1,2,1,5,5,1,1,3,2,2,1,2,5,1,1,3,5,3,3,6,3
%N A387422 The length of the maximal common prefix of the binary expansions of n and sigma(n), where sigma is the sum of divisors function.
%H A387422 Antti Karttunen, <a href="/A387422/b387422.txt">Table of n, a(n) for n = 1..65537</a>
%H A387422 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>.
%H A387422 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.
%F A387422 a(n) = (1+A000523(n)) - A387423(n).
%o A387422 (PARI) A387422(n) = { my(a=binary(n), b=binary(sigma(n)), i=1); while(i<=#a,if(a[i]!=b[i],return(i-1)); i++); (#a); };
%Y A387422 Cf. A000203, A000523, A387423.
%Y A387422 Cf. also A347380, A387412.
%K A387422 nonn,base,new
%O A387422 1,6
%A A387422 _Antti Karttunen_, Sep 01 2025