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Search: id:A163845
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| 1, 13, 109, 765, 4881, 29369, 169919, 956237, 5272945, 28632525, 153638211, 816715073, 4309138419, 22598433555, 117926579385, 612863125965, 3174156512865
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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a(n) = sum{k=0..n} sum{i=k..n} binomial(n-k,n-i)*(2i+1)$
where i$ denotes the swinging factorial of i (A056040).
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LINKS
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Peter Luschny, Swinging Factorial.
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MAPLE
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swing := proc(n) option remember; if n = 0 then 1 elif
irem(n, 2) = 1 then swing(n-1)*n else 4*swing(n-1)/n fi end:
a := proc(n) local i, k; add(add(binomial(n-k, n-i)*swing(2*i+1), i=k..n), k=0..n) end:
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CROSSREFS
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Cf. A163842.
Sequence in context: A142040 A002648 A055840 this_sequence A075143 A005769 A042941
Adjacent sequences: A163842 A163843 A163844 this_sequence A163846 A163847 A163848
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KEYWORD
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nonn
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AUTHOR
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Peter Luschny (peter(AT)luschny.de), Aug 06 2009
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