This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A369831 #11 Feb 12 2024 12:41:47
%S A369831 1,1,1,6,23,120,720,5040,40320,362880
%N A369831 a(n) is the number of distinct values of the permanent of an n X n symmetric Toeplitz matrix using the integers 1 to n.
%H A369831 Wikipedia, <a href="http://en.wikipedia.org/wiki/Toeplitz_matrix">Toeplitz Matrix</a>.
%F A369831 a(n) <= A000142(n).
%F A369831 Conjectured e.g.f.: 1/(1 - x) - x^2/2 - x^4/24.
%t A369831 a[n_] := CountDistinct[Table[Permanent[ToeplitzMatrix[Part[Permutations[Range[n]],i]]], {i, n!}]]; Join[{1}, Array[a,9]]
%o A369831 (Python)
%o A369831 from itertools import permutations
%o A369831 from sympy import Matrix
%o A369831 def A369831(n): return len({Matrix([p[i:0:-1]+p[:n-i] for i in range(n)]).per() for p in permutations(range(1,n+1))}) # _Chai Wah Wu_, Feb 12 2024
%Y A369831 Cf. A000142, A351019, A351020.
%Y A369831 Cf. A369830, A369832, A369833, A369834, A369835.
%K A369831 nonn,hard,more
%O A369831 0,4
%A A369831 _Stefano Spezia_, Feb 03 2024