A381197 a(n) = numerator( [(x*y*z*u)^n] 1/sqrt(1 - (x + y + z + u*(x*y + x*z + y*z))) ).
1, 9, 1575, 107415, 143918775, 13539797271, 5492167201521, 586937023583625, 4173054453859037175, 477630312182609961375, 223908157536370130248425, 26751307348701533866638825, 51959852697049291288154030625, 6393039919009116988875533492625, 3182668486503393355366954041669375
Offset: 0
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.
Programs
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Mathematica
a[n_]:=Numerator[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]