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A138525
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a(n) = Sum_{k=0..n} (2*k)!.
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5
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1, 3, 27, 747, 41067, 3669867, 482671467, 87660962667, 21010450850667, 6423384156578667, 2439325392333218667, 1126440053169940898667, 621574841786409380258667, 403913035968392044964258667
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OFFSET
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0,2
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COMMENTS
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Last digit is 7 for n > 2. Therefore there is no square in this sequence except 1. - Altug Alkan, Dec 01 2015
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LINKS
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MAPLE
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MATHEMATICA
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PROG
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(PARI) a(n) = sum(k=0, n, (2*k)!); \\ Altug Alkan, Dec 01 2015
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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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EXTENSIONS
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STATUS
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approved
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