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A089709
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a(1) = 1, a(2) = 2; for n>2, a(n) = sum_{r=1..n} {sum of all previous terms taken r at a time}.
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1
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1, 2, 6, 36, 360, 6480, 220320, 14541120, 1890345600, 487709164800, 250682510707200, 257200255985587200, 527260524770453760000, 2160713630509319508480000, 17704887488393364052485120000
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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a(4) = [{a(1)} + {a(2)} + {a(3)}] + [{(a(1) + a(2)} + {a(1) + a(3)} + { a(2) + a(3)}] + [{a(1) + a(2) + a(3)}] = 36.
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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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