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A156016
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Expansion of (1-x-sqrt(1-6x-3x^2))/(2x).
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1
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1, 3, 9, 36, 162, 783, 3969, 20817, 112023, 615033, 3431403, 19398690, 110880900, 639730305, 3720657807, 21790419444, 128398625658, 760668489729, 4528069760691, 27070491820644, 162464919528222, 978463778897637
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OFFSET
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0,2
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COMMENTS
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Transform of Catalan numbers by Riordan array ((1+x)/(1-x), x(1+x)/(1-x)^2).
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LINKS
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Table of n, a(n) for n=0..21.
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FORMULA
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a(n)=sum{k=0..n, sum{j=0..k+1, C(k+1,j)*C(n+k-j,n-k-j)}*A000108(k)}.
a(n+1)=3*A107264(n). [From Philippe DELEHAM, Feb 04 2009]
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CROSSREFS
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Cf. A100239.
Sequence in context: A185162 A106435 A058540 * A032314 A144352 A107895
Adjacent sequences: A156013 A156014 A156015 * A156017 A156018 A156019
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry, Feb 01 2009
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STATUS
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approved
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