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A279120 Numerators of coefficients in expansion of 1/(1 + 2 cos(sqrt(x))). 3
1, 1, 1, 7, 809, 1847, 7943, 6921461, 126235201, 1258024561, 2288629046003, 80348736972167, 111111638337011, 40453941942593304589, 258227002122139705201, 7316538113501035554721, 34747165199239302488636803, 2962605017328303351107945687 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Clark Kimberling, Table of n, a(n) for n = 0..999

EXAMPLE

1/3 + (1/9)x + (1/36)x^2 + (7/1080)x^3 + ... ; 1/3, 1/9, 1/36, 7/1080, 809/544320, ... = A279120/A279121.

MATHEMATICA

z = 30; t = CoefficientList[Series[1/(1 + 2 Cos[Sqrt[x]]), {x, 0, z}], x];

Numerator[t];  (* A279120 *)

Denominator[t];  (* A279121 *)

(1/3) Denominator[t] ; (* A279122 *)

CROSSREFS

Cf. A279121, A279122.

Sequence in context: A014013 A001467 A278438 * A047788 A251698 A203694

Adjacent sequences:  A279117 A279118 A279119 * A279121 A279122 A279123

KEYWORD

nonn,easy,frac

AUTHOR

Clark Kimberling, Dec 07 2016

STATUS

approved

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Last modified May 26 19:44 EDT 2019. Contains 323597 sequences. (Running on oeis4.)