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A025249 (1/2)*s(n+3), where s = A025248. 1
1, 1, 3, 7, 13, 29, 71, 163, 377, 913, 2219, 5375, 13189, 32677, 81167, 202523, 508273, 1280537, 3236275, 8207543, 20880893, 53263405, 136205527, 349137811, 896881641, 2308523809, 5953138875, 15378562415, 39791453685, 103115768885, 267597960095 (list; graph; refs; listen; history; internal format)
OFFSET

1,3

FORMULA

G.f.: (1-x-4*x^3-sqrt(1-2*x+x^2-8*x^3))/(4*x^3) - Michael Somos, Jun 08, 2000.

PROG

(PARI) a(n)=polcoeff((-sqrt(1-2*x+x^2-8*x^3+x^4*O(x^n)))/4, n+3)

CROSSREFS

Sequence in context: A161490 A134270 A091565 * A147098 A109291 A199218

Adjacent sequences:  A025246 A025247 A025248 * A025250 A025251 A025252

KEYWORD

nonn

AUTHOR

Clark Kimberling (ck6(AT)evansville.edu)

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Last modified February 16 15:57 EST 2012. Contains 205935 sequences.