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Search: id:A047831
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| A047831 |
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a(n)=Product_{i=1..n} ((i+5)*(i+6)*(i+7)*(i+8)*(i+9))/(i*(i+1)*(i+2)*(i+3)*(i+4)). |
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2
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| 1, 252, 19404, 731808, 16818516, 267227532, 3184461423, 30107635272, 235234907908, 1566039386912, 9095857138368, 46960429261824, 218772384397632, 931020034054176, 3656383418054268, 13365232267026024, 45800747571406905, 148055097314224100
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Number of tilings of a <5,n,5> hexagon.
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REFERENCES
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O. D. Anderson, Find the next sequence, J. Rec. Math., 8 (No. 4, 1975-1976), 241.
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FORMULA
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a(n)=C(n,n-1)*C(n+1,n-2)*C(n+2,n-3)*C(n+3,n-4)*C(n+4,n-5)/(140*5!), n>=5 . - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 29 2007
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MAPLE
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seq(binomial(n, n-1)*binomial(n+1, n-2)*binomial(n+2, n-3)*binomial(n+3, n-4)*binomial(n+4, n-5)/(140*5!), n=5..22); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 29 2007
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CROSSREFS
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Fifth row of array A103905.
Sequence in context: A151610 A024018 A109924 this_sequence A076013 A078263 A109929
Adjacent sequences: A047828 A047829 A047830 this_sequence A047832 A047833 A047834
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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).
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EXTENSIONS
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Definition corrected by Daniel Soll (soll(AT)mathematik.uni-marburg.de), Aug 31 2004
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