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 A054013 #11 Oct 27 2023 22:00:46
%S A054013 0,0,0,2,0,5,0,6,3,7,0,3,0,9,8,14,0,2,0,1,10,13,0,11,5,15,12,27,0,11,
%T A054013 0,30,14,19,12,18,0,21,16,9,0,11,0,39,32,25,0,27,7,42,20,45,0,11,16,7,
%U A054013 22,31,0,47,0,33,40,62,18,11,0,57,26,3,0,50,0,39,48,63,18,11,0,25,39,43,0
%N A054013 Chowla function of n read modulo n.
%C A054013 Chowla's function (A048050) = sum of divisors of n except 1 and n.
%H A054013 Antti Karttunen, <a href="/A054013/b054013.txt">Table of n, a(n) for n = 1..16384</a>
%F A054013 a(n) = A048050(n) mod n
%p A054013 with(numtheory): [seq((sigma(i) - i - 1) mod i, i=2..100)];
%t A054013 Table[Mod[DivisorSigma[1,n]-n-1,n],{n,90}] (* _Harvey P. Dale_, Dec 01 2011 *)
%o A054013 (PARI) A054013(n) = ((sigma(n)-n-1) % n); \\ _Antti Karttunen_, Oct 30 2017
%Y A054013 Cf. A048050, A054014, A054015.
%K A054013 nonn
%O A054013 1,4
%A A054013 _Asher Auel_, Jan 17 2000