A374069 a(n) is the permanent of the symmetric Toeplitz matrix of order n whose element (i,j) equals the |i-j|-th composite or 1 if i = j.

1, 1, 17, 261, 8393, 356618, 20355656, 1498310848, 141920467648, 16632516446720, 2345863766165536, 394823892589979472, 78653652638945445776, 18216229760067802231488, 4833321599094565894295552, 1462259517864407783009737728, 498935238969900279377677930496, 190227655207141695023381769820864

Offset: 0

Author

Stefano Spezia, Jun 27 2024

Keywords

• nonn

Examples

			a(4) = 8393:
  [1, 4, 6, 8]
  [4, 1, 4, 6]
  [6, 4, 1, 4]
  [8, 6, 4, 1]
		

Crossrefs

Cf. A071080 (determinant).

Cf. A374067, A374068, A374070, A374071.

Programs

Mathematica

Composite[n_Integer]:=FixedPoint[n + PrimePi[ # ] + 1 &, n + PrimePi[n] + 1]; a[n_] := Permanent[Table[If[i == j, 1, Composite[Abs[i - j]]], {i, 1, n}, {j, 1, n}]]; Join[{1},Array[a,17]]

PARI

c(n) = for(k=0, primepi(n), isprime(n++)&&k--); n; \\ A002808
a(n) = matpermanent(matrix(n, n, i, j, if (i==j, 1, c(abs(i-j))))); \\ Michel Marcus, Jun 27 2024