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 A380297 #6 Jan 20 2025 12:51:06
%S A380297 1,1,4,135,403200,2778300000,483930961920000,7180239749742259200000,
%T A380297 5799315033741817236160512000000,
%U A380297 6429886152366060611794081018183680000000,466736302504188801174703321606427057848320000000000,23001739511849592885668155296556060490333421994770432000000000
%N A380297 Denominators of the determinant of matrix (M(n) - H(n)), where H(n) is the n-th Hilbert matrix and M(n) is an n X n matrix with i,j-th entry i+j-1.
%t A380297 a[n_]:=Denominator[Det[Table[(i+j-1) - 1/(i+j-1),{i,n},{j,n}]]]; Join[{1},Array[a,11]]
%o A380297 (PARI) a(n) = denominator(matdet(matrix(n, n, i, j, (i+j-1) - 1/(i+j-1)))); \\ _Michel Marcus_, Jan 19 2025
%Y A380297 Cf. A061913 (numerators).
%K A380297 nonn,frac
%O A380297 0,3
%A A380297 _Stefano Spezia_, Jan 19 2025