A248749 - OEIS

A248749

Decimal expansion of limit of the real part of f(1+i,n), where f(x,0) = 1 and f(x,n) = x + 1/f(x,n-1).

1, 5, 2, 9, 0, 8, 5, 5, 1, 3, 6, 3, 5, 7, 4, 6, 1, 2, 5, 1, 6, 0, 9, 9, 0, 5, 2, 3, 7, 9, 0, 2, 2, 5, 2, 1, 0, 6, 1, 9, 3, 6, 5, 0, 4, 9, 8, 3, 8, 9, 0, 9, 7, 4, 3, 1, 4, 0, 7, 7, 1, 1, 7, 6, 3, 2, 0, 2, 3, 9, 8, 1, 1, 5, 7, 9, 1, 8, 9, 4, 6, 2, 7, 7, 1, 1

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OFFSET

1,2

COMMENTS

See A046854 for a triangle of coefficients of the numerators and denominators of f(x,n). Note that the limit of f(1,n) is the golden ratio.

LINKS

Table of n, a(n) for n=1..86.

FORMULA

Equals (1+sqrt(2+sqrt(5)))/2. - Vaclav Kotesovec, Oct 19 2014

EXAMPLE

limit = 1.52908551363574612516099052379022521061936504983890974314077117

63202398115791894627711485520734841970516965799404...

n f(n,x) Re(f(n,1+i)) Im(f(n,1+i))

1 1 1 0

2 1 + x 2 1

3 (1 + x + x^2)/ (1 + x) 7/5 4/5

4 (1 + 2x + x^2 + x^3)/(1 + x + x^2) 20/13 9/13

Re(f(11,1+i) = 815/533 = 1.529162...

Im(f(11,1+i) = 396/533 = 0.742964...

MAPLE

evalf((1+sqrt(2+sqrt(5)))/2, 120); # Vaclav Kotesovec, Oct 19 2014

MATHEMATICA

$RecursionLimit = Infinity; $MaxExtraPrecision = Infinity;

f[x_, n_] := x + 1/f[x, n - 1]; f[x_, 1] = 1; t = Table[Factor[f[x, n]], {n, 1, 12}]; u = t /. x -> I + 1; {Re[u], Im[u]}

{N[Re[u], 12], N[Im[u], 12]}

t = Table[Factor[f[x, n]], {n, 1, 300}]; u = t /. x -> I + 1;

r1 = N[Re[u][[300]], 130]

r2 = N[Im[u][[300]], 130]

d1 = RealDigits[r1] (* A248749 *)

d2 = RealDigits[r2] (* A248750 *)

CROSSREFS

Cf. A248750, A046854.

Sequence in context: A078335 A021658 A270859 * A248751 A021193 A010483

Adjacent sequences: A248746 A248747 A248748 * A248750 A248751 A248752

KEYWORD

nonn,easy,cons

AUTHOR

Clark Kimberling, Oct 13 2014

STATUS

approved