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Search: id:A089709
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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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+0
2
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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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FORMULA
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a(n)=(2^(n-2)+2)*a(n-1), n>3. - Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 17 2003
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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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Cf. A089985.
Sequence in context: A061302 A133822 A133892 this_sequence A055512 A078973 A152480
Adjacent sequences: A089706 A089707 A089708 this_sequence A089710 A089711 A089712
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 14 2003
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EXTENSIONS
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More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 21 2003
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