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1, 1, 2, 2, 2, 6, 4, 20, 10, 70, 28, 252, 84, 924, 264, 3432, 858, 12870, 2860, 48620, 9724, 184756, 33592, 705432, 117572, 2704156, 416024, 10400600, 1485800, 40116600, 5348880, 155117520, 19389690, 601080390, 70715340, 2333606220, 259289580, 9075135300
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,3
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COMMENTS
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LINKS
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FORMULA
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a(n) = 2*floor(n/2)*(n-2)!/floor(n/2)!^2 for n>=2.
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MAPLE
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if n < 2 then 1
else 2*iquo(n, 2)*(n-2)!/iquo(n, 2)!^2
fi end:
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CROSSREFS
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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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