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Search: id:A056040
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| A056040 |
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a(n)=n!/x^2, where x=Floor[n/2]! |
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+0
2
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| 1, 2, 6, 6, 30, 20, 140, 70, 630, 252, 2772, 924, 12012, 3432, 51480, 12870, 218790, 48620, 923780, 184756, 3879876, 705432, 16224936, 2704156, 67603900, 10400600, 280816200, 40116600, 1163381400, 155117520, 4808643120, 601080390
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Similar to but different from A001405.
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FORMULA
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E.g.f.: (1+x)*BesselI(0, 2*x). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 19 2004
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EXAMPLE
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n=10: a(10)=10!/5!^2=binomial(10,5); n=11: a(11)=11!/5!^2=6*binomial(11,5)
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CROSSREFS
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Cf. A000142, A001405, A000188, A055772, A056042.
Bisections are A000984 and A002457.
Sequence in context: A070889 A072744 A056042 this_sequence A099566 A147299 A090549
Adjacent sequences: A056037 A056038 A056039 this_sequence A056041 A056042 A056043
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jul 25 2000
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