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A272551
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Number of singular vector tuples for a general 4-dimensional n X n X n X n tensor.
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5
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1, 24, 997, 51264, 2940841, 180296088, 11559133741, 765337680384, 51921457661905, 3590122671128664, 252070718210663749, 17922684123178825536, 1287832671004683373753, 93368940577497932331288, 6821632357294515590873917, 501741975445243527381995520, 37121266623211130111114816929
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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a[n_] := Module[{a, b, c, d, s}, s = Series[(
((a + b + c)^n - d^n)*
((b + c + d)^n - a^n)*
((c + d + a)^n - b^n)*
((d + a + b)^n - c^n))/(
(a + b + c - d)*
(b + c + d - a)*
(c + d + a - b)*
(d + a + b - c)),
{a, 0, n}, {b, 0, n}, {c, 0, n}, {d, 0, n}] // Normal // Expand;
Cases[List @@ s, k_Integer a^(n-1) b^(n-1) c^(n-1) d^(n-1)] /. (a|b|c|d) -> 1 // First
];
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CROSSREFS
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See A271905 for the three-dimensional analog.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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