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%I #18 May 23 2021 07:11:25
%S 1,5,30,276,3165,47521,826000,16843792,387723045,10009889889,
%T 285360865350,8918311872516,302888304741841,11112685595264369,
%U 437898699063881208,18447025862624951488,827242515246907227633,39346558373191515582161
%N a(n) = Sum_{1 <= x_1, x_2, ... , x_n <= n} gcd(x_1,x_2, ... ,x_n).
%H Seiichi Manyama, <a href="/A344525/b344525.txt">Table of n, a(n) for n = 1..386</a>
%F a(n) = Sum_{k=1..n} phi(k) * floor(n/k)^n.
%F a(n) ~ n^n. - _Vaclav Kotesovec_, May 23 2021
%t a[n_] := Sum[EulerPhi[k] * Quotient[n, k]^n, {k, 1, n}]; Array[a, 20] (* _Amiram Eldar_, May 22 2021 *)
%o (PARI) a(n) = sum(k=1, n, eulerphi(k)*(n\k)^n);
%Y Main diagonal of A344479.
%Y Cf. A018806, A344140, A344522, A344523, A344524.
%K nonn
%O 1,2
%A _Seiichi Manyama_, May 22 2021
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