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 A307654 #24 May 13 2021 02:35:20
%S A307654 1,-3,-26,-3,-3124,78,-823542,-3,-26,9372,-285311670610,78,
%T A307654 -302875106592252,2470626,81224,-3,-827240261886336764176,78,
%U A307654 -1978419655660313589123978,9372,21412092,855935011830,-20880467999847912034355032910566,78,-3124,908625319776756,-26,2470626
%N A307654 a(n) = Product_{p|n, p prime} (1 - p^p).
%H A307654 Seiichi Manyama, <a href="/A307654/b307654.txt">Table of n, a(n) for n = 1..388</a>
%e A307654 a(6) = (1 - 2^2) * (1 - 3^3) = 78.
%t A307654 f[p_, e_] := 1 - p^p; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 28] (* _Amiram Eldar_, May 13 2021 *)
%Y A307654 Cf. A023900, A307653, A321222.
%K A307654 sign
%O A307654 1,2
%A A307654 _Seiichi Manyama_, Apr 20 2019