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Search: id:A134171
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| A134171 |
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(9/2)*(n-1)*(n-2)*(n-3). |
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+0
4
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| 0, 0, 0, 27, 108, 270, 540, 945, 1512, 2268, 3240, 4455, 5940, 7722, 9828, 12285, 15120, 18360, 22032, 26163, 30780, 35910, 41580, 47817, 54648, 62100, 70200, 78975, 88452, 98658, 109620, 121365, 133920, 147312, 161568, 176715, 192780, 209790, 227772, 246753
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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Number of n permutations (n>=3) of 4 objects u, v, z, x with repetition allowed, containing n-3=0 u's. Example: if n=3 then n-3 =zero u, a()=27 because we have vzx, vxz, zvx, zxv, xvz, xzv, vvv, zzz, xxx, vvx, vxv, xvv, xxv, xvx, vxx, vvz, vzv, zvv, zzv, zvz, vzz, xzz, zxz, zzx, xxz, xzx, zxx. A027465 formatted as a triangular array: diagonal: 27,108,270,540,945,1512 [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 06 2008]
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REFERENCES
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Zvonkine D., Counting ramified coverings and intersection theory on Hurwitz spaces II (local structure of Hurwitz spaces and combinatorial results). Moscow Mathematical Journal, vol. 7 (2007), no. 1, 135-162.
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LINKS
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D. Zvonkine, Home Page
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FORMULA
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C(n+2,3)*3^3, n>=-2 [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 06 2008]
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MAPLE
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seq(binomial(n, n-3)*3^3, n=0..39); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 18 2008
seq(binomial(n+2, 3)*3^3, n=-2..22) [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 06 2008]
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CROSSREFS
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A027468 A008585, A027465 [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 06 2008]
Sequence in context: A158549 A044278 A044659 this_sequence A129026 A042426 A042424
Adjacent sequences: A134168 A134169 A134170 this_sequence A134172 A134173 A134174
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Jan 30 2008
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