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Search: id:A129619
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| A129619 |
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a(n) = largest proper divisor of the sum of all positive integers which are <= n and are not included among the first n-1 terms of the sequence. |
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+0
1
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| 1, 1, 1, 3, 1, 1, 12, 16, 1, 17, 31, 31, 25, 1, 52, 52, 52, 61, 47, 23, 91, 102, 102, 114, 114, 127, 1, 103, 169, 184, 184, 200, 1, 1, 251, 269, 115, 1, 326, 346, 1, 155, 409, 431, 1, 1, 1, 143, 525, 550, 1, 1, 602, 629, 101, 37, 463, 1, 753, 783, 783, 814, 89, 585, 910, 943
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OFFSET
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1,4
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EXAMPLE
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The positive integers which are <= 8 and do not occur among the first 7 terms of the sequence are 2,4,5,6,7,8. a(8) is the largest proper divisor of the sum of these integers. 2+4+5+6+7+8 = 32. So a(8) is the largest proper divisor of 32, which is 16.
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MATHEMATICA
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a = {1}; For[n = 2, n < 70, n++, AppendTo[a, Divisors[n*(n + 1)/2 - Plus @@ Select[Union[a, a], # < n + 1 &]][[ -2]]]]; a - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Nov 21 2007
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CROSSREFS
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Sequence in context: A098778 A078122 A128592 this_sequence A094573 A055154 A015112
Adjacent sequences: A129616 A129617 A129618 this_sequence A129620 A129621 A129622
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), May 30 2007
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Nov 21 2007
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