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