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A292440 Expansion of (1 - x + sqrt(1 - 2*x - 3*x^2))/2 in powers of x. 2
1, -1, -1, -1, -2, -4, -9, -21, -51, -127, -323, -835, -2188, -5798, -15511, -41835, -113634, -310572, -853467, -2356779, -6536382, -18199284, -50852019, -142547559, -400763223, -1129760415, -3192727797, -9043402501, -25669818476, -73007772802 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Apart from a(1) the same as A168051. - R. J. Mathar, Sep 18 2017

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

FORMULA

Convolution inverse of A001006.

Let f(x) = (1 - x - sqrt(1 - 2*x - 3*x^2))/(2*x^2).

G.f.: 1-x-x^2/(1-x-x^2/(1-x-x^2/(1-x-x^2/(1-x-x^2/(... (continued fraction).

G.f.: 1/f(x) = 1 - x - x^2*f(x).

a(n) = -A001006(n-2) for n > 1.

a(n) ~ -3^(n - 1/2) / (2*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Aug 14 2018

MATHEMATICA

CoefficientList[Series[(1-x +Sqrt[1-2*x-3*x^2])/2, {x, 0, 50}], x] (* G. C. Greubel, Aug 13 2018 *)

PROG

(PARI) x='x+O('x^50); Vec((1 - x + sqrt(1 - 2*x - 3*x^2))/2) \\ G. C. Greubel, Aug 13 2018

(MAGMA) m:=50; R<x>:=PowerSeriesRing(Rationals(), m); Coefficients(R!((1-x +Sqrt(1-2*x-3*x^2))/2)); // G. C. Greubel, Aug 13 2018

CROSSREFS

Cf. A001006, A086246.

Sequence in context: A094288 A168051 A166587 * A168049 A001006 A086246

Adjacent sequences:  A292437 A292438 A292439 * A292441 A292442 A292443

KEYWORD

sign

AUTHOR

Seiichi Manyama, Sep 16 2017

STATUS

approved

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Last modified October 18 18:10 EDT 2018. Contains 316323 sequences. (Running on oeis4.)