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Search: id:A025265
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| A025265 |
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a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 4. |
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+0
2
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| 1, 0, 1, 2, 4, 9, 22, 56, 146, 388, 1048, 2869, 7942, 22192, 62510, 177308, 506008, 1451866, 4185788, 12119696, 35227748, 102753800, 300672368, 882373261, 2596389190, 7658677856, 22642421206, 67081765932, 199128719896, 592179010350, 1764044315540
(list; graph; listen)
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OFFSET
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1,4
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FORMULA
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G.f.: (1-sqrt(1-4*x+4*x^2-4*x^3))/2 - Michael Somos, Jun 08, 2000.
G.f. A(x) satisfies 0=f(x, A(x)) where f(x, y)=(x-x^2+x^3)-(y-y^2) . - Michael Somos May 26 2005
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PROGRAM
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(PARI) a(n)=polcoeff((1-sqrt(1-4*x+4*x^2-4*x^3+x*O(x^n)))/2, n)
(PARI) a(n)=if(n<1, 0, polcoeff(subst(serreverse(x-x^2+x*O(x^n)), x, x-x^2+x^3), n))
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CROSSREFS
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A091561(n)=a(n+2).
Adjacent sequences: A025262 A025263 A025264 this_sequence A025266 A025267 A025268
Sequence in context: A055588 A088456 A091561 this_sequence A037245 A130018 A099754
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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)
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