A106476 Sequence array of Euler phi function.

1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 4, 2, 2, 1, 1, 2, 4, 2, 2, 1, 1, 6, 2, 4, 2, 2, 1, 1, 4, 6, 2, 4, 2, 2, 1, 1, 6, 4, 6, 2, 4, 2, 2, 1, 1, 4, 6, 4, 6, 2, 4, 2, 2, 1, 1, 10, 4, 6, 4, 6, 2, 4, 2, 2, 1, 1, 4, 10, 4, 6, 4, 6, 2, 4, 2, 2, 1, 1, 12, 4, 10, 4, 6, 4, 6, 2, 4, 2, 2, 1, 1, 6, 12, 4, 10, 4, 6, 4, 6, 2, 4, 2, 2, 1, 1

Offset: 0

Author

Paul Barry, May 03 2005

Keywords

• easy
• nonn
• tabl

Comments

Row sums are A002088(n+1). Diagonal sums are A106477. Riordan array (1/Sum_{j>=0} A106479(j)*x^j, x).

Examples

			Triangle begins:
  1;
  1,1;
  2,1,1;
  2,2,1,1;
  4,2,2,1,1;
  2,4,2,2,1,1;
		

Crossrefs

Cf. A000010, A002088, A106477, A106478, A106479, A106480.

Programs

Mathematica

T[n_, k_] := If[k <= n, EulerPhi[n - k + 1], 0]; Table[T[n, k], {n, 0, 13}, {k, 0, n}] // Flatten (* Amiram Eldar, Nov 16 2024 *)

Formula

Triangle T(n, k) = if(k <= n, phi(n-k+1), 0).