A369947 a(n) is the maximal determinant of an n X n Hankel matrix using the first 2*n - 1 prime numbers.

1, 2, 11, 286, 86087, 9603283, 1764195984

Offset

0,2

Links

Table of n, a(n) for n=0..6.

Wikipedia, Hankel matrix.

Example

a(2) = 11:
  3, 2;
  2, 5.
a(3) = 286:
   3, 11, 5;
  11,  5, 7;
   5,  7, 2.
a(4) = 86087:
   7,  3, 13, 17;
   3, 13, 17,  2;
  13, 17,  2, 11;
  17,  2, 11,  5.

Mathematica

a[n_] := Max[Table[Det[HankelMatrix[Join[Drop[per = Part[Permutations[Prime[Range[2 n - 1]]], i], n], {Part[per, n]}], Join[{Part[per, n]}, Drop[per, - n]]]], {i, (2 n - 1) !}]]; Join[{1}, Array[a, 5]]

Prog

(PARI) a(n) = my(v=[1..2*n-1], m=-oo, d); forperm(v, p, d = matdet(matrix(n, n, i, j, prime(p[i+j-1]))); if (d>m, m = d)); m; \\ Michel Marcus, Feb 08 2024
(Python)
from itertools import permutations
from sympy import primerange, prime, Matrix
def A369947(n): return max(Matrix([p[i:i+n] for i in range(n)]).det() for p in permutations(primerange(prime((n<<1)-1)+1))) if n else 1 # Chai Wah Wu, Feb 12 2024

Crossrefs

Cf. A024356, A368352.

Cf. A369946 (minimal), A350933 (maximal absolute value), A369949, A350940 (maximal permanent).

Sequence in context: A072386 A185122 A350932 * A198894 A367798 A222206

Adjacent sequences: A369944 A369945 A369946 * A369948 A369949 A369950

Keyword

nonn,hard,more

Author

Stefano Spezia, Feb 06 2024

Extensions

a(6) from Michel Marcus, Feb 08 2024

Status

approved