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 A382998 #12 Apr 12 2025 09:37:34
%S A382998 1,-1,11,-66,629,-7750,117655,-2097676,43046889,-999990036,
%T A382998 25937424611,-743008622708,23298085122493,-793714765724686,
%U A382998 29192926025492783,-1152921504875290680,48661191875666868497,-2185911559727680349982,104127350297911241532859
%N A382998 a(n) = Sum_{d|n} phi(n/d) * (-n)^(d-1).
%F A382998 a(n) = (1/n) * A382997(n).
%F A382998 a(n) = Sum_{k=1..n} (-n)^(gcd(n,k) - 1).
%F A382998 a(n) = [x^n] Sum_{k>=1} phi(k) * log(1 + n*x^k) / k.
%F A382998 a(n) = [x^n] Sum_{k>=1} phi(k) * x^k / (1 + n*x^k).
%o A382998 (PARI) a(n) = sumdiv(n, d, eulerphi(n/d)*(-n)^(d-1));
%Y A382998 Main diagonal of A382993.
%Y A382998 Main diagonal of A382995.
%Y A382998 Cf. A000010, A382997, A383003.
%K A382998 sign
%O A382998 1,3
%A A382998 _Seiichi Manyama_, Apr 12 2025