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Search: id:A039721
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| A039721 |
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a[ 1 ]=1,a[ m+1 ]=2*sum{k=1 to floor((m+1)/2)} a[ m+1-k ]. |
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+0
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| 1, 2, 4, 12, 32, 96, 280, 840, 2496, 7488, 22400, 67200, 201408, 604224, 1812112, 5436336, 16307328, 48921984, 146760960, 440282880, 1320833664, 3962500992, 11887458176, 35662374528, 106986989184, 320960967552, 962882499840
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OFFSET
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1,2
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FORMULA
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a[ 1 ]=1, a[ 2 ]=2, a[ 2m+1 ]=3a[ 2m ]-2a[ m ], a[ 2m+2 ]=3a[ 2m+1 ] (m is positive integer.)
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EXAMPLE
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a[ 6 ]=2*(a[ 5 ]+a[ 4 ]+a[ 3 ])=2*(32+12+4)=96
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CROSSREFS
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Adjacent sequences: A039718 A039719 A039720 this_sequence A039722 A039723 A039724
Sequence in context: A026151 A025178 A087211 this_sequence A002528 A027695 A005028
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KEYWORD
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easy,nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com)
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), May 04 2000
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