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A015013
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q-factorial numbers for q=-2.
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3
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1, -1, -3, 15, 165, -3465, -148995, 12664575, 2165642325, -738484032825, -504384594419475, 688484971382583375, 1880252456845835197125, -10268058666835106011499625, -112158004817839862963610403875
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) = Product_{k=1..n} ((-2)^k - 1) / (-2 - 1).
a(n) = (-1)^(floor((n mod 4)/2)) * Product_{k=1..n} A001045(k). - Altug Alkan, Apr 05 2016
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MATHEMATICA
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RecurrenceTable[{a[1]==1, a[n]==(((-2)^n - 1) * a[n-1])/(-3)}, a, {n, 15}]
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PROG
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(Magma) I:=[1]; [n le 1 select I[n] else (((-2)^n - 1) * Self(n-1))/(-3): n in [1..18]]; // Vincenzo Librandi, Oct 26 2012
(PARI) a(n) = prod(k=1, n, ((-2)^k-1)/(-3)) \\ Michel Marcus, Apr 05 2016
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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