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A374390 a(n) is the maximal permanent of an n X n symmetric Toeplitz matrix having 0 on the main diagonal and all the first n-1 primes off-diagonal.

%I A374390 #5 Jul 07 2024 13:49:06
%S A374390 1,0,4,36,1936,144260,31972988,6800311204,2560967581304,
%T A374390 975834087080060,557171087172087364
%N A374390 a(n) is the maximal permanent of an n X n symmetric Toeplitz matrix having 0 on the main diagonal and all the first n-1 primes off-diagonal.
%H A374390 Wikipedia, <a href="https://en.wikipedia.org/wiki/Toeplitz_matrix">Toeplitz Matrix</a>.
%e A374390 a(5) = 144260:
%e A374390   [0, 7, 5, 3, 2]
%e A374390   [7, 0, 7, 5, 3]
%e A374390   [5, 7, 0, 7, 5]
%e A374390   [3, 5, 7, 0, 7]
%e A374390   [2, 3, 5, 7, 0]
%t A374390 a[n_]:=Max[Table[Permanent[ToeplitzMatrix[Join[{0},Part[Permutations[Prime[Range[n-1]]],i]]]],{i,(n-1)!}]]; Join[{1},Array[a,10]]
%Y A374390 Cf. A374345.
%Y A374390 Cf. A374386, A374387, A374388, A374389.
%Y A374390 Cf. A374068 (minimal permanent).
%K A374390 nonn,hard,more
%O A374390 0,3
%A A374390 _Stefano Spezia_, Jul 07 2024