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A108490
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Expansion of 1/sqrt(1-4x-8x^2-24x^3+36x^4).
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0
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1, 2, 10, 56, 268, 1448, 7864, 42752, 236368, 1313696, 7339552, 41217920, 232321984, 1313731712, 7449834880, 42347380736, 241225384192, 1376662561280, 7869527190016, 45051709749248, 258256281078784, 1482218578159616
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| In general, sum{k=0..n, C(n-k,k)^2*a^k*b^(n-k)} has expansion 1/sqrt(1-2bx-(2ab-b^2)x^2-2a*b^2*x^3+(ab)^2*x^4).
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FORMULA
| a(n)=sum{k=0..n, C(n-k, k)^2*3^k*2^(n-k)}.
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MATHEMATICA
| CoefficientList[Series[1/Sqrt[1-4x-8x^2-24x^3+36x^4], {x, 0, 30}], x] (* From Harvey P. Dale, Mar 13 2011 *)
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CROSSREFS
| Cf. A108486.
Sequence in context: A152395 A175935 A122826 * A165817 A000172 A097971
Adjacent sequences: A108487 A108488 A108489 * A108491 A108492 A108493
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Jun 04 2005
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