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Search: id:A014432
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| A014432 |
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a(n) = Sum( a(i)a(n-1-i),{i,1,n-1} ), with a(0) = 1, a(1) = 3. |
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3
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| 1, 3, 3, 12, 30, 111, 363, 1353, 4917, 18777, 71769, 280506, 1103556, 4395009, 17622309, 71220828, 289510662, 1183627137, 4862148753, 20061888924, 83100910530, 345457823493, 1440734205513, 6026408186457, 25275954499905, 106277040064191
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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G.f.: (1+x-sqrt(1-2*x-11*x^2))/2 - Michael Somos, Jun 08, 2000.
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MAPLE
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seq(coeff(convert(series((1+x-sqrt(1-2*x-11*x^2))/(2*x), x, 50), polynom), x, i), i=0..30); A014431:=proc(n) options remember: local i: if n<2 then RETURN([1, 3][n+1]) else RETURN(add(A014431(i)*A014431(n-1-i), i=1..n-1)) fi:end; seq(A014431(n), n=0..30); (C. Ronaldo)
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PROGRAM
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(PARI) a(n)=polcoeff((1+x-sqrt(1-2*x-11*x^2+x*O(x^n)))/2, n)
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CROSSREFS
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Cf. A025237.
Sequence in context: A161804 A097342 A025236 this_sequence A107330 A076509 A020550
Adjacent sequences: A014429 A014430 A014431 this_sequence A014433 A014434 A014435
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KEYWORD
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nonn
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AUTHOR
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Wouter Meeussen (wouter.meeussen(AT)pandora.be)
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EXTENSIONS
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Corrected by C. Ronaldo (aga_new_ac(AT)hotmail.com) and Ralf Stephan, Dec 19 2004
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