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Search: id:A133106
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| A133106 |
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Number of Ferrers diagrams with a single Ferrers puncture with the same orientation inscribed strictly inside with half-perimeter=n. |
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+0
2
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| 1, 8, 41, 168, 602, 1968, 6021, 17512, 48950, 132496, 349258, 900368, 2277556, 5667936, 13906221, 33695208, 80746846, 191601872, 450642654, 1051472048, 2435679852, 5605044640, 12820922530, 29164511376, 66004709148, 148678206880
(list; graph; listen)
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OFFSET
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8,2
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LINKS
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Arvind Ayyer (ayyer(AT)physics.rutgers.edu), Sep 11 2007, Table of n, a(n) for n = 8..91
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FORMULA
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a(n)=[(2*n^2-16*n+6)*a(n-1)+(4*n^2-68*n+240)*a(n-2)-(8*n^2-88*n+240)*a(n-3)]/(n^2-14*n+48) with a(6)=0, a(7)=0, a(8)=1. G.F.=(1-(1-4*x^2)^(1/2))*x^6/(2*(2*x-1)^4)
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EXAMPLE
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The sequence starts with n=8 because the smallest such object whose cartoon is below has a perimeter of 16. (1 denotes cell outside the puncture and 2 denotes cell inside the puncture).
111
121
111
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CROSSREFS
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Cf. A057410, A057406, A133107.
Sequence in context: A120646 A041116 A135797 this_sequence A078797 A156790 A080840
Adjacent sequences: A133103 A133104 A133105 this_sequence A133107 A133108 A133109
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KEYWORD
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easy,nonn
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AUTHOR
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Arvind Ayyer (ayyer(AT)physics.rutgers.edu), Sep 11 2007
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