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Search: id:A081123
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| 1, 1, 1, 1, 2, 2, 6, 6, 24, 24, 120, 120, 720, 720, 5040, 5040, 40320, 40320, 362880, 362880, 3628800, 3628800, 39916800, 39916800, 479001600, 479001600, 6227020800, 6227020800, 87178291200, 87178291200, 1307674368000
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OFFSET
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0,5
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FORMULA
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a(n) = (floor(n/2))!
E.g.f.: 1+sqrt(Pi)/2*(x+2)*exp(x^2/4)*erf(x/2). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Sep 25 2003
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MAPLE
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seq(seq(k!, j=0..1), k=0..15); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 10 2007
with (combinat):a:=n->mul(fibonacci(2, i+1), i=0..n/2):seq(a(n), n=-2..28); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 25 2008
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CROSSREFS
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Cf. A081124, A004526, A081125.
Adjacent sequences: A081120 A081121 A081122 this_sequence A081124 A081125 A081126
Sequence in context: A135401 A129881 A132369 this_sequence A056038 A076929 A062073
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Mar 07 2003
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