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 A143729 #4 Jul 22 2025 06:11:06
%S A143729 1,1,-2,-2,-4,-4,-3,-14,-13,-9,0,-22,-11,-31
%N A143729 Sum of termwise product of mu(k) and reduced residue system k mod n.
%F A143729 a(n) = Sum_{1<=k<=n, GCD(k,n)=1} mu(k)*k. Equals row sums of triangle A143728.
%e A143729 a(7) = -3 since the relative primes of 7 (Cf. row 7, triangle A127368) = (1, 2, 3, 4, 5, 6, 0). We apply the termwise product of mu(k), where mu(k) = A008683: (1, -1, -1, 0, -1, 1, -1,...) getting row 7 of triangle A143728: (1, -2, -3, 0, -5, 6, 0), sum = -3.
%Y A143729 Cf. A008683, A143728, A127368
%K A143729 sign
%O A143729 1,3
%A A143729 _Gary W. Adamson_, Aug 30 2008