OFFSET
1,2
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} Fibonacci(2*k-1)/(2*k)!.
Equals (2 * cosh(phi) + (3+sqrt(5))*cosh(1/phi))/(5+sqrt(5)), where phi is the golden ratio (A001622). (End)
EXAMPLE
1.5906097564064614629697931199995829165183536750...
MATHEMATICA
f[x_] := Cosh[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, 300}], 100]
RealDigits[u0, 10]
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Clark Kimberling, Jul 14 2011
STATUS
approved