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Search: id:A086871
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| 1, 2, 10, 58, 370, 2514, 17850, 130890, 983650, 7536418, 58648810, 462306266, 3683602130, 29620138994, 240059315610, 1958940281322, 16081662931650, 132723191430210, 1100568370427850, 9164925012016506, 76612776253995570
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Hankel transform is A165928. [From Paul Barry (pbarry(AT)wit.ie), Sep 30 2009]
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REFERENCES
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C. Coker, Enumerating a class of lattice paths, Discrete Math., 271 (2003), 13-28.
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FORMULA
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G.f.: (1-x-sqrt((1-x)(1-9x)))/(4x)=2/(1+sqrt((1-9x)/(1-x)))=y satisfies 0=(1-x)(1-y)+2xy^2. - Michael Somos Mar 06 2004
Moment representation: a(n)=(1/(4*pi))*Int(x^n*sqrt(-x^2+10x-9)/x,x,1,9)+(1/2)*0^n [From Paul Barry (pbarry(AT)wit.ie), Sep 30 2009]
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PROGRAM
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(PARI) a(n)=if(n<0, 0, polcoeff(2/(1+sqrt((1-9*x)/(1-x)+x*O(x^n))), n)) - Michael Somos Mar 06 2004
(PARI) a(n)=if(n<1, n==0, n++; 2*polcoeff(serreverse(x*(1-4*x)/(1-3*x)+x*O(x^n)), n)) - Michael Somos Mar 06 2004
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CROSSREFS
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2*A059231(n)=a(n), if n>0.
Sequence in context: A093303 A075870 A074608 this_sequence A108450 A112369 A124964
Adjacent sequences: A086868 A086869 A086870 this_sequence A086872 A086873 A086874
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Sep 16 2003
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EXTENSIONS
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More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 17 2003
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