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 A367552 #13 Nov 22 2023 10:48:28
%S A367552 0,9,512,50706,7962624,1838528498,587068342272,248158343164707,
%T A367552 134217728134217728,90438270904261473426,74300837068800000000000,
%U A367552 73119374851006048408704228,84922087747184192618514874368,114943537906488487820754156670578
%N A367552 a(n) = Sum_{d|n} (d^2-1)^n.
%F A367552 a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(n,k) * sigma_{2*k}(n).
%t A367552 a[n_]:= Sum[(-1)^(n-k)*Binomial[n,k]*DivisorSigma[2*k,n],{k,0,n}]; Array[a,14] (* _Stefano Spezia_, Nov 22 2023 *)
%o A367552 (PARI) a(n) = sumdiv(n, d, (d^2-1)^n);
%Y A367552 Cf. A163191, A367551.
%K A367552 nonn
%O A367552 1,2
%A A367552 _Seiichi Manyama_, Nov 22 2023