A106201 Expansion of Re(x/(1-x-2*i*x^2)), i=sqrt(-1).

0, 1, 1, 1, 1, -3, -11, -23, -39, -43, -3, 129, 417, 877, 1349, 1305, -407, -5627, -16243, -32079, -46287, -37987, 35285, 236873, 623609, 1162293, 1559837, 1009889, -2034495, -9728051, -23660955, -41633415, -51467895, -22390171, 101331373, 391586577, 887713361, 1473400829, 1653762805, 267778473, -4669059303, -15499500395

Offset

0,6

Comments

Imaginary part is A106202.

Links

Table of n, a(n) for n=0..41.

Index entries for linear recurrences with constant coefficients, signature (2,-1,0,-4)

Formula

G.f.: x*(1-x)/(1-2*x+x^2+4*x^4).

a(n) = sum(k=0..floor((n-1)/2), C(n-k-1, k)*2^k*cos(pi*k/2) ).

Mathematica

LinearRecurrence[{2, -1, 0, -4}, {0, 1, 1, 1}, 50] (* Harvey P. Dale, May 22 2020 *)

Crossrefs

Cf. A104862, A014292.

Sequence in context: A072671 A320901 A119173 * A132209 A142463 A289575

Adjacent sequences: A106198 A106199 A106200 * A106202 A106203 A106204

Keyword

easy,sign

Author

Paul Barry, Apr 25 2005

Status

approved