A391790 a(n) is the permanent of the n-th order Hankel matrix M(n) whose generic element is given by M(i,j) = phi(i+j) with i,j = 0, ..., n-1 and M(0,0) = 0.

1, 0, 1, 7, 154, 4860, 265048, 15959744, 1702784480, 174374326912, 25548068301056, 4392451231078400, 975899333856328192, 222438109032688009216, 67405846484696921661440, 20031561030571606152773632, 7508762497888891587398205440, 3261123198022796670658670166016

Offset

0,4

Links

Table of n, a(n) for n=0..17.

Wikipedia, Hankel matrix.

Example

a(4) = 154:
  [0, 1, 1, 2]
  [1, 1, 2, 2]
  [1, 2, 2, 4]
  [2, 2, 4, 2]

Mathematica

a[n_]:=Permanent[Table[EulerPhi[i+j], {i, 0, n-1}, {j, 0, n-1}]]; Join[{1}, Array[a, 17]]

Crossrefs

Cf. A000010, A368026, A391788, A391789 (determinant).

Sequence in context: A219102 A219981 A213113 * A384750 A144683 A229711

Adjacent sequences: A391787 A391788 A391789 * A391791 A391792 A391793

Keyword

nonn

Author

Stefano Spezia, Dec 20 2025

Status

approved