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Search: id:A085458
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| A085458 |
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a(0)=1, for n>0: a(n)=4 Sum(C(2i+1,i)C(n-1,n-1-i)(-1)^(n-1-i)2^i,(i=0,..,n-1)). |
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+0
1
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| 1, 4, 20, 116, 708, 4452, 28532, 185300, 1215268, 8030404, 53381844, 356577588, 2391430020, 16092704292, 108605848116, 734783381652, 4982063186916, 33844621986180, 230306722637204, 1569571734301172, 10711405584991300
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Sum(Sum (-1)^(n-i)a(j)a(i-j),(j=0,..,i)),(i=0,..,n)=7^n
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FORMULA
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G.f.: A(x)= sqrt((1 + x)/(1 - 7x))
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MATHEMATICA
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CoefficientList[Series[Sqrt[(1 + x)/(1 - 7x)], {x, 0, 25}], x]
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CROSSREFS
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Sequence in context: A100034 A106567 A077445 this_sequence A085456 A120915 A100328
Adjacent sequences: A085455 A085456 A085457 this_sequence A085459 A085460 A085461
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KEYWORD
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easy,nonn
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AUTHOR
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Mario Catalani (mario.catalani(AT)unito.it), Jul 02 2003
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