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Search: id:A130317
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| A130317 |
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Smallest number having exactly n triangular divisors. |
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+0
3
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| 1, 3, 6, 36, 30, 90, 180, 210, 420, 630, 1890, 1260, 2520, 6930, 18480, 20790, 13860, 27720, 41580, 83160, 138600, 245700, 235620, 180180, 556920, 360360, 540540, 1670760, 1081080, 1413720, 2702700, 2162160, 6486480, 3063060, 8288280
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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2*a(n) is smallest number having exactly n oblong divisors.
A007862(a(n)) = n and A007862(m) <> n for m < a(n).
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LINKS
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Ray Chandler, Table of n, a(n) for n=1..58
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FORMULA
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a(n) = A088726(n-1)/2 for n>1. - Chandler
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EXAMPLE
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a(3)=6: A007862(6)=#{1,2*(2+1)/2,3*(3+1)/2}=3;
a(4)=36: A007862(36)=#{1,2*(2+1)/2,3*(3+1)/2,8*(8+1)/2}=4;
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CROSSREFS
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Cf. A130279.
Sequence in context: A134748 A068904 A009197 this_sequence A019467 A119186 A119115
Adjacent sequences: A130314 A130315 A130316 this_sequence A130318 A130319 A130320
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 23 2007
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jun 24 2008
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