OFFSET
0,1
COMMENTS
Reduction of a function f(x) by a substitution q(x)->s(x) is introduced at A193010.
FORMULA
From Amiram Eldar, Jan 18 2022: (Start)
Equals Sum_{k>=1} (-1)^k*Fibonacci(2*k)/(2*k)!.
Equals -2*sin(1/2)*sin(sqrt(5)/2)/sqrt(5). (End)
EXAMPLE
-0.3856051379557488291513243591721325...
MATHEMATICA
f[x_] := Cos[x]; r[n_] := Fibonacci[n];
c[n_] := SeriesCoefficient[Series[f[x], {x, 0, n}], n]
u1 = N[Sum[c[n]*r[n], {n, 0, 300}], 100]
RealDigits[u1, 10]
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Clark Kimberling, Jul 14 2011
STATUS
approved