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Search: id:A014431
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| A014431 |
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a(1) = 1, a(2) = 2, a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-2)*a(2) for n >= 3. |
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+0
3
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| 1, 2, 2, 6, 14, 42, 122, 382, 1206, 3922, 12914, 43190, 145950, 498170, 1714026, 5940014, 20712646, 72623266, 255875298, 905477734, 3216853294, 11469069258, 41023019098, 147166210014, 529374272470, 1908965352434, 6899707805522
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n)=2*A025235(n-2) for n>=2.
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FORMULA
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G.f.: (1+x-sqrt(1-2x-7x^2))/2. - Michael Somos, Jun 08 2000.
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PROGRAM
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(PARI) a(n)=polcoeff((1+x-sqrt(1-2*x-7*x^2+x*O(x^n)))/2, n)
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CROSSREFS
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Sequence in context: A002203 A097341 A142710 this_sequence A142471 A071208 A083555
Adjacent sequences: A014428 A014429 A014430 this_sequence A014432 A014433 A014434
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu) and Wouter Meeussen (wouter.meeussen(AT)pandora.be)
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EXTENSIONS
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Corrected by T. D. Noe (noe(AT)sspectra.com), Oct 31 2006
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