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A181540 a(n) = Sum_{k=0..n} gcd(n,k)*phi(k). 2

%I #21 Jul 12 2020 10:18:46

%S 0,1,3,8,13,26,29,54,59,84,93,142,139,202,195,244,259,352,327,444,433,

%T 508,505,656,639,776,719,866,889,1054,1057,1208,1151,1332,1255,1624,

%U 1575,1728,1579,1886,2011,2130,2159,2348,2329,2716,2329

%N a(n) = Sum_{k=0..n} gcd(n,k)*phi(k).

%C Row sums of triangle A181538.

%p A181540 := n -> add(igcd(n,k)*numtheory[phi](k),k=0..n);

%t Table[Sum[GCD[n,k]EulerPhi[k],{k,0,n}],{n,0,50}] (* _Harvey P. Dale_, Jul 12 2020 *)

%o (PARI) a(n) = sum(k=1, n, gcd(n, k)*eulerphi(k)); \\ _Michel Marcus_, May 18 2018

%Y Cf. A181538.

%K nonn

%O 0,3

%A _Peter Luschny_, Oct 29 2010

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Last modified April 24 00:30 EDT 2024. Contains 371917 sequences. (Running on oeis4.)