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Search: id:A033876
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| A033876 |
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Expansion of (1/2x)*(1/(1-4*x)^(3/2)-1). |
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+0
5
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| 3, 15, 70, 315, 1386, 6006, 25740, 109395, 461890, 1939938, 8112468, 33801950, 140408100, 581690700, 2404321560, 9917826435, 40838108850, 167890003050, 689232644100, 2825853840810, 11572544300460
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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a(n) is the trace of the zigzag matrix Z(n+1) (see A088961). - Paul Boddington (psb(AT)maths.warwick.ac.uk), Nov 03 2003
The number of edges in the odd graph O_k (for k >= 2) can be computed as 0.5*(2k-1)*C(2k-2,k-1). This sequence gives the number of edges in O_k for integer values of k from k=2. - Kailasam Viswanathan Iyer ( kvi(AT)nitt.edu ), Mar 04 2009
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FORMULA
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a(n) = (2*n+3)*binomial(2*n+1, n). - Paul Boddington (psb(AT)maths.warwick.ac.uk), Nov 03 2003
Equals n*A000984/4, n >= 2. - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 04 2007
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MAPLE
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[seq(n*binomial(2*n, n)/4, n=2..22)]; - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 04 2007
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CROSSREFS
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Cf. A000984. A001803. A002457. A088961.
Sequence in context: A086200 A122558 A110211 this_sequence A009174 A123942 A155117
Adjacent sequences: A033873 A033874 A033875 this_sequence A033877 A033878 A033879
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Jeffrey Shallit
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