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 A369945 #18 Feb 12 2024 13:42:19
%S A369945 1,1,3,39,1710,128502,13644965
%N A369945 a(n) is the number of distinct values of the permanent of an n X n Hankel matrix using the integers 0 to 2*(n - 1).
%H A369945 Wikipedia, <a href="https://en.wikipedia.org/wiki/Hankel_matrix">Hankel matrix</a>.
%t A369945 a[n_] := CountDistinct[Table[Permanent[HankelMatrix[Join[Drop[per = Part[Permutations[Range[0, 2 n - 2]], i], n],{Part[per, n]}], Join[{Part[per, n]}, Drop[per, - n]]]], {i, (2 n - 1) !}]]; Join[{1},Array[a, 5]]
%o A369945 (PARI) a(n) = my(v=[0..2*n-2], list=List()); forperm(v, p, listput(list, matpermanent(matrix(n, n, i, j, p[i+j-1])));); #Set(list); \\ _Michel Marcus_, Feb 08 2024
%o A369945 (Python)
%o A369945 from itertools import permutations
%o A369945 from sympy import Matrix
%o A369945 def A369945(n): return len({Matrix([p[i:i+n] for i in range(n)]).per() for p in permutations(range((n<<1)-1))}) # _Chai Wah Wu_, Feb 12 2024
%Y A369945 Cf. A358569, A358570.
%K A369945 nonn,hard,more
%O A369945 0,3
%A A369945 _Stefano Spezia_, Feb 06 2024
%E A369945 a(6) from _Michel Marcus_, Feb 08 2024