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Search: id:A106183
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| A106183 |
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Expansion of 1/sqrt(1-4x-4x^2+16x^3). |
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+0
2
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| 1, 2, 8, 24, 88, 304, 1120, 4096, 15328, 57536, 218112, 830208, 3176704, 12196352, 46982144, 181452800, 702465536, 2724948992, 10589474816, 41217216512, 160657903616, 627019489280, 2449986043904, 9583049572352, 37519931654144
(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 A067804. In general, a(n)=sum{k=0..floor(n/2), C(2k,k)C(2(n-2k),n-2k)*r^k} has g.f. 1/sqrt(1-4x-4r*x^2+16r*x^3).
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FORMULA
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a(n)=sum{k=0..floor(n/2), C(2k, k)C(2(n-2k), n-2k)}.
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CROSSREFS
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Sequence in context: A094038 A007223 A106189 this_sequence A060899 A123775 A052624
Adjacent sequences: A106180 A106181 A106182 this_sequence A106184 A106185 A106186
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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), Apr 24 2005
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