A381198 a(n) = denominator( [(x*y*z*u)^n] 1/sqrt(1 - (x + y + z + u*(x*y + x*z + y*z))) ).

1, 4, 64, 256, 16384, 65536, 1048576, 4194304, 1073741824, 4294967296, 68719476736, 274877906944, 17592186044416, 70368744177664, 1125899906842624, 4503599627370496, 4611686018427387904, 18446744073709551616, 295147905179352825856, 1180591620717411303424, 75557863725914323419136

Offset: 0

Author

Stefano Spezia, Feb 16 2025

Keywords

• nonn
• frac

Comments

Apparently a duplicate of A110258 and A056982. - R. J. Mathar, Feb 18 2025

Links

• S. Hassani, J.-M. Maillard, and N. Zenine, On the diagonals of rational functions: the minimal number of variables (unabridged version), arXiv:2502.05543 [math-ph], 2025. See p. 24.

Crossrefs

Cf. A268554, A381197 (numerators).

Programs

Mathematica

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]