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 A300824 #10 Mar 24 2018 18:55:16 %S A300824 0,0,0,2,0,2,0,0,0,4,0,4,0,8,2,8,0,6,0,-2,6,4,0,8,2,2,0,0,0,8,0,6,2, %T A300824 10,8,12,0,20,0,28,0,18,0,16,6,22,0,22,6,22,8,24,0,18,4,8,18,4,0,16,0, %U A300824 2,18,2,2,26,0,4,20,0,0,24,0,2,28,0,8,30,0,-2,0,4,0,0,10,8,2,16,0,24,6,16,0,22,20,14,0,14,6,40,0,26,0,32,24 %N A300824 Difference between A300222(n) and its Möbius transform. %H A300824 Antti Karttunen, <a href="/A300824/b300824.txt">Table of n, a(n) for n = 1..65537</a> %F A300824 a(n) = A300222(n) - A300822(n). %F A300824 a(n) = -Sum_{d|n, d<n} A008683(n/d)*A300222(d) = Sum_{d|n, d<n} A300822(d). %F A300824 a(n) = A051953(n) - A300823(n). %t A300824 f[n_] := FromDigits[IntegerDigits[n, 3] /. 1 -> 0, 3]; Table[f@ n - DivisorSum[n, MoebiusMu[n/#] f@ # &], {n, 105}] (* _Michael De Vlieger_, Mar 17 2018 *) %o A300824 (PARI) %o A300824 A300222(n) = fromdigits(apply(x->(if (1==x, 0, x)), digits(n, 3)), 3); %o A300824 A300824(n) = -sumdiv(n,d,(d<n)*moebius(n/d)*A300222(d)); %Y A300824 Cf. A008683, A051953, A300222, A300822, A300823, A300825. %K A300824 sign,base %O A300824 1,4 %A A300824 _Antti Karttunen_, Mar 14 2018