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Search: id:A115217
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| A115217 |
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Diagonal sums of "correlation triangle" for 2^n. |
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+0
2
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| 1, 2, 6, 13, 30, 62, 133, 270, 558, 1125, 2286, 4590, 9253, 18542, 37230, 74533, 149358, 298862, 598309, 1196910, 2394990, 4790565, 9583470, 19168110, 38340901, 76684142, 153377646, 306759973, 613538670, 1227086702, 2454210853
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Diagonal sums of number triangle A003983.
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FORMULA
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a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, [j<=k]*2^(k-j)[j<=n-2k]2^(n-2k-j)}}.
G.f.: 1/((1-2x)(1-2x^2)(1-x^3)); a(n)=2a(n-1)+2a(n-2)-3a(n-3)-2a(n-4)-2a(n-5)+4a(n-6); - Paul Barry (pbarry(AT)wit.ie), Jan 18 2006
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CROSSREFS
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Sequence in context: A034465 A055243 A075632 this_sequence A094687 A018013 A062424
Adjacent sequences: A115214 A115215 A115216 this_sequence A115218 A115219 A115220
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Jan 16 2006
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