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Search: id:A070960
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| A070960 |
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a(1) = 1; a(n) = n!*(3/2) for n>=2. |
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+0
3
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| 1, 3, 9, 36, 180, 1080, 7560, 60480, 544320, 5443200, 59875200, 718502400, 9340531200, 130767436800, 1961511552000, 31384184832000, 533531142144000, 9603560558592000, 182467650613248000, 3649353012264960000
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Let g be a permutation of [1..n] having say j_i cycles of length i, with Sum_i i*j_i = n; sequence gives Sum_{g} Sum_{i} (j_1 + j_2). - N. J. A. Sloane, Jul 22 2009
a(n) is the greatest integer that can be obtained from the integers {1, 2, 3, ..., n} using each number at most once and the operators +, -, *, /.
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LINKS
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Index entries for similar sequences
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FORMULA
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E.g.f.: x*(2+x)/(1-x)/2. - Vladeta Jovovic (vladeta(AT)eunet.rs), Dec 15 2002
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EXAMPLE
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a(5)=180 because the greatest number we can obtain using 1,2,3,4,5 is 180 which is (1+2)*3*4*5.
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MATHEMATICA
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s=3; lst={1, s}; Do[s+=n*s+s; AppendTo[lst, s], {n, 1, 5!, 1}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Nov 08 2008]
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CROSSREFS
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Cf. A000142, A060315.
Sequence in context: A032314 A144352 A107895 this_sequence A030834 A030893 A030936
Adjacent sequences: A070957 A070958 A070959 this_sequence A070961 A070962 A070963
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KEYWORD
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easy,nonn
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AUTHOR
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Koksal Karakus (karakusk(AT)hotmail.com), May 24 2002
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EXTENSIONS
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Edited by N. J. A. Sloane, Jul 22 2009
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