A279120 Numerators of coefficients in expansion of 1/(1 + 2 cos(sqrt(x))).

1, 1, 1, 7, 809, 1847, 7943, 6921461, 126235201, 1258024561, 2288629046003, 80348736972167, 111111638337011, 40453941942593304589, 258227002122139705201, 7316538113501035554721, 34747165199239302488636803, 2962605017328303351107945687

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: A338968 A342834 A278438 * A047788 A251698 A203694

Adjacent sequences: A279117 A279118 A279119 * A279121 A279122 A279123

Keyword

nonn,easy,frac

Author

Clark Kimberling, Dec 07 2016

Status

approved