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A358603
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a(n) = Sum_{k=0..floor(n/2)} (-1)^k * (n-k)!/(n-2*k)!.
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4
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1, 1, 0, -1, 0, 3, 2, -9, -12, 35, 78, -153, -544, 723, 4170, -3337, -35028, 10851, 320678, 57255, -3178152, -2190253, 33864546, 42120183, -385314460, -719159517, 4649508222, 12033407591, -59076411312, -204022615725, 784134861818, 3554417974647, -10768948801764
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OFFSET
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0,6
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LINKS
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FORMULA
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a(n) = (a(n-1) - n * a(n-2) + 1)/2 for n > 1.
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PROG
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(PARI) a(n) = sum(k=0, n\2, (-1)^k*(n-k)!/(n-2*k)!);
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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