A106477 Diagonal sums of Euler phi function sequence array.

1, 1, 3, 3, 7, 5, 13, 9, 19, 13, 29, 17, 41, 23, 49, 31, 65, 37, 83, 45, 95, 55, 117, 63, 137, 75, 155, 87, 183, 95, 213, 111, 233, 127, 257, 139, 293, 157, 317, 173, 357, 185, 399, 205, 423, 227, 469, 243, 511, 263, 543, 287, 595, 305, 635, 329, 671, 357, 729, 373

Offset: 0

Author

Paul Barry, May 03 2005

Keywords

• easy
• nonn

Comments

Diagonal sums of A106476.

Crossrefs

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

Programs

Mathematica

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

Formula

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