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A116396
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Expansion of 2/((2+x)*sqrt(1-4*x)-x).
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1
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1, 2, 7, 25, 93, 353, 1358, 5273, 20614, 81003, 319584, 1264924, 5019743, 19963699, 79541181, 317406302, 1268283199, 5073605801, 20316709251, 81427911966, 326612013623, 1310968893954, 5265285993860, 21158914176719, 85071253608611
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Diagonal sums of number triangle A116395.
Diagonal sums of the Riordan matrix ((1-sqrt(1-4x))/(2x*sqrt(1-4x)),(1-sqrt(1-4x))/(2*sqrt(1-4x))) (A035324) [Emanuele Munarini, Apr 26 2011]
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FORMULA
| a(n)=sum{k=0..floor(n/2), (4^(n-k)/2^k)*sum{j=0..k, C(k,j)C(n-k+(j-1)/2,n-k)(-1)^(k-j)}}.
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MATHEMATICA
| CoefficientList[Series[(x+(2+x)Sqrt[1-4x])/(2-6x-8x^2-2x^3), {x, 0, 25}], x]) [Emanuele Munarini, Apr 26 2011]
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CROSSREFS
| Sequence in context: A074605 A108081 A199247 * A150453 A150454 A150455
Adjacent sequences: A116393 A116394 A116395 * A116397 A116398 A116399
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Feb 12 2006
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