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Search: id:A141245
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| A141245 |
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Numerators in expansion of (1+x-sqrt(1-x^2))/(x(1-x)). |
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1
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| 1, 3, 3, 13, 13, 27, 27, 221, 221, 449, 449, 1817, 1817, 3667, 3667, 59101, 59101, 118917, 118917, 478099, 478099, 960397, 960397, 7712569, 7712569, 15477141, 15477141, 62094289, 62094289, 124522883, 124522883, 3994427101
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OFFSET
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0,2
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COMMENT
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The denominators in the expansion of (1+x-sqrt(1-x^2))/(x(1-x)) are 1,2,2,8,8,16,16,....
The sequence 1,3/2,3/2,13/8,13/8,... is the image of 2n+1 under the
Chebyshev related (rational) Riordan array c((x/2)^2),(x/2)c((x/2)^2)) with c(x) the g.f. of A000108.
The Hankel transform of fraction sequence is (-1)^n*(2n+1)/4^comb(n+1,2).
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CROSSREFS
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Cf. A141244.
Sequence in context: A076509 A020550 A135949 this_sequence A147032 A146261 A146176
Adjacent sequences: A141242 A141243 A141244 this_sequence A141246 A141247 A141248
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KEYWORD
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easy,frac,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Jun 17 2008
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