A025249 - OEIS

A025249

a(n) = (1/2)*s(n+3), where s = A025248.

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

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..31.

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

Conjecture: +(n+3)*a(n) +(-2*n-3)*a(n-1) +n*a(n-2) +4*(-2*n+3)*a(n-3)=0. - R. J. Mathar, Feb 25 2015

PROG

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

CROSSREFS

Cf. A025248.

Sequence in context: A260022 A134270 A091565 * A147098 A109291 A340067

Adjacent sequences: A025246 A025247 A025248 * A025250 A025251 A025252

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved