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A290044
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a(n) = |Sum_{k=0..n} (-1)^k*(2k)!!|.
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1
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1, 1, 7, 41, 343, 3497, 42583, 602537, 9719383, 176075177, 3539816023, 78209790377, 1883780763223, 49127973630377, 1379201149390423, 41470672541233577, 329725285558734423, 45290937289840177577, 1633052915424520654423, 62144013487721190961577
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OFFSET
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0,3
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COMMENTS
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a(20) = 19 * 47 * 73 * 54470291 * 700938921577. Thus a(n) are multiples of 19 for n >= 20.
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LINKS
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MATHEMATICA
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Table[Abs@ Sum[(-1)^k*(2 k)!!, {k, 0, n}], {n, 0, 19}] (* Michael De Vlieger, Jul 19 2017 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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