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%I #17 Mar 13 2021 10:05:10
%S 1,3,11,68,629,7791,117655,2097224,43046745,1000000637,25937424611,
%T 743008378618,23298085122493,793714773371811,29192926025391919,
%U 1152921504608944272,48661191875666868497,2185911559738739594277,104127350297911241532859
%N a(n) = Sum_{k=1..n} gcd(k,n)^(gcd(k,n) - 1).
%H Seiichi Manyama, <a href="/A342436/b342436.txt">Table of n, a(n) for n = 1..387</a>
%F a(n) = Sum_{d|n} phi(n/d) * d^(d-1).
%t a[n_] := Sum[GCD[k, n]^(GCD[k, n] - 1), {k, 1, n}]; Array[a, 20] (* _Amiram Eldar_, Mar 12 2021 *)
%o (PARI) a(n) = sum(k=1, n, gcd(k, n)^(gcd(k, n)-1));
%o (PARI) a(n) = sumdiv(n, d, eulerphi(n/d)*d^(d-1));
%Y Cf. A000010, A056665, A342421, A342423, A342435.
%K nonn
%O 1,2
%A _Seiichi Manyama_, Mar 12 2021