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Search: id:A025247
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A025247 a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-3)*a(3) for n >= 4. +0
3
2, 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)
OFFSET

1,1
FORMULA

G.f.: (1+2*x-sqrt(1-4*x+4*x^2-4*x^3))/2 - Michael Somos, Jun 08, 2000.

PROGRAM

(PARI) a(n)=polcoeff((2*x-sqrt(1-4*x+4*x^2-4*x^3+x*O(x^n)))/2, n)

CROSSREFS

Sequence in context: A071496 A071502 A074704 this_sequence A127767 A055509 A006667

Adjacent sequences: A025244 A025245 A025246 this_sequence A025248 A025249 A025250

KEYWORD

nonn

AUTHOR

Clark Kimberling (ck6(AT)evansville.edu)

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.

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