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 A381198 #13 Feb 19 2025 13:37:59
%S A381198 1,4,64,256,16384,65536,1048576,4194304,1073741824,4294967296,
%T A381198 68719476736,274877906944,17592186044416,70368744177664,
%U A381198 1125899906842624,4503599627370496,4611686018427387904,18446744073709551616,295147905179352825856,1180591620717411303424,75557863725914323419136
%N A381198 a(n) = denominator( [(x*y*z*u)^n] 1/sqrt(1 - (x + y + z + u*(x*y + x*z + y*z))) ).
%C A381198 Apparently a duplicate of A110258 and A056982. - _R. J. Mathar_, Feb 18 2025
%H A381198 S. Hassani, J.-M. Maillard, and N. Zenine, <a href="https://arxiv.org/abs/2502.05543">On the diagonals of rational functions: the minimal number of variables (unabridged version)</a>, arXiv:2502.05543 [math-ph], 2025. See p. 24.
%t A381198 a[n_]:=Denominator[SeriesCoefficient[1/Sqrt[1-(x+y+z+u*(x*y+x*z+y*z))],{x,0,n},{y,0,n},{z,0,n},{u,0,n}]]; Array[a,15,0]
%Y A381198 Cf. A268554, A381197 (numerators).
%K A381198 nonn,frac
%O A381198 0,2
%A A381198 _Stefano Spezia_, Feb 16 2025