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 A381244 #9 Feb 18 2025 19:00:05
%S A381244 1,1,2,12,3696
%N A381244 Number of regions in the arrangement of hyperplanes corresponding to the nonzero differences of two permutations of order n.
%C A381244 The number of distinct hyperplanes is given by A381243.
%o A381244 (Sage) def a381244(n): return HyperplaneArrangements(QQ,tuple(f'x{i}' for i in range(n)))([[list(r),0] for p in Permutations(n) for r in Permutations([p[i]-i-1 for i in range(n)]) if vector(r)>0]).n_regions()
%Y A381244 Cf. A019589, A175176, A362968, A381243.
%K A381244 nonn,more,hard
%O A381244 0,3
%A A381244 _Max Alekseyev_, Feb 17 2025