OFFSET
1,1
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 1 + Sum_{k>=1} 2^(2*k)*Fibonacci(2*k-1)/(2*k)!.
Equals ((3+sqrt(5))*cosh(1-sqrt(5)) + 2*cosh(1+sqrt(5)))/(5 + sqrt(5)). (End)
EXAMPLE
4.8707186334008057368566594211377757838921196937...
MATHEMATICA
f[x_] := Cosh[2 x]; r[n_] := Fibonacci[n];
c[n_] := SeriesCoefficient[Series[f[x], {x, 0, n}], n]
u0 = N[Sum[c[n]*r[n - 1], {n, 0, 100}], 100]
RealDigits[u0, 10]
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Clark Kimberling, Jul 15 2011
STATUS
approved