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A086894
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a(n) = (A000522(2*n) + 1)/2.
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1
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1, 3, 33, 979, 54801, 4932051, 651030673, 118487582403, 28437019776609, 8701728051642211, 3306656659624040001, 1527675376746306480243, 843276807963961177093873, 548129925176574765111017139, 414386223433490522423928956721, 360516014387136754508818192346851
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = (1 + (2*n)!*Sum_{k=0..2*n} 1/k!)/2. - Andrew Howroyd, Jan 05 2020
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PROG
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(PARI) a(n)={(1 + sum(k=0, 2*n, (2*n)!/k!))/2} \\ Andrew Howroyd, Jan 05 2020
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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