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%I #7 Mar 29 2015 16:22:45
%S 2,5,10,20,36,74,134,272,526,1052,2058,4160,8204,16466,32824,65696,
%T 131088,262490,524306,1049168,2097316,4195358,8388630,16779632,
%U 33554516,67112996,134218282,268443848,536870940,1073759432,2147483678
%N a(n) = (1/n)*Sum_{k=1..n} k*2^gcd(n,k).
%F a(n) = (A000079(n) + n*A000031(n))/2.
%t f[n_] := Sum[k*2^GCD[n, k], {k, n}]/n; Table[ f[n], {n, 32}] (* _Robert G. Wilson v_, Feb 12 2005 *)
%K easy,nonn
%O 1,1
%A _Vladeta Jovovic_, Feb 03 2005
%E More terms from _Robert G. Wilson v_, Feb 12 2005