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Diagonal sums of Euler phi function sequence array.
6

%I #7 Nov 16 2024 02:58:01

%S 1,1,3,3,7,5,13,9,19,13,29,17,41,23,49,31,65,37,83,45,95,55,117,63,

%T 137,75,155,87,183,95,213,111,233,127,257,139,293,157,317,173,357,185,

%U 399,205,423,227,469,243,511,263,543,287,595,305,635,329,671,357,729,373

%N Diagonal sums of Euler phi function sequence array.

%C Diagonal sums of A106476.

%F a(n) = Sum{k=0..floor(n/2)} phi(n-2k+1).

%t a[n_] := Sum[EulerPhi[n - 2*k + 1], {k, 0, Floor[n/2]}]; Array[a, 60, 0] (* _Amiram Eldar_, Nov 16 2024 *)

%Y Cf. A000010, A106476, A106478, A106479, A106480.

%K easy,nonn

%O 0,3

%A _Paul Barry_, May 03 2005