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 A382997 #8 Apr 12 2025 09:37:29
%S A382997 1,-2,33,-264,3145,-46500,823585,-16781408,387422001,-9999900360,
%T A382997 285311670721,-8916103472496,302875106592409,-11112006720145604,
%U A382997 437893890382391745,-18446744078004650880,827240261886336764449,-39346408075098246299676,1978419655660313589124321
%N A382997 a(n) = -Sum_{d|n} phi(n/d) * (-n)^d.
%F A382997 a(n) = -Sum_{k=1..n} (-n)^gcd(n,k).
%o A382997 (PARI) a(n) = -sumdiv(n, d, eulerphi(n/d)*(-n)^d);
%Y A382997 Main diagonal of A382994.
%Y A382997 Cf. A000010, A383010.
%K A382997 sign
%O A382997 1,2
%A A382997 _Seiichi Manyama_, Apr 12 2025