A270745 (r,1)-greedy sequence, where r(k) = k/tau^k and tau = golden ratio.

1, 3, 6, 63, 18292, 822680526, 810795400558456607, 3059608561526409532580548135921262544, 41330361304323764432512049819825720283867354602583921458622085452146872094

Offset

1,2

Comments

Let x > 0, and let r = (r(k)) be a sequence of positive irrational numbers. Let a(1) be the least positive integer m such that r(1)/m < x, and inductively let a(n) be the least positive integer m such that r(1)/a(1) + ... + r(n-1)/a(n-1) + r(n)/m < x. The sequence (a(n)) is the (r,x)-greedy sequence. We are interested in choices of r and x for which the series r(1)/a(1) + ... + r(n)/a(n) + ... converges to x. See A270744 for a guide to related sequences.

Links

Table of n, a(n) for n=1..9.

Formula

a(n) = ceiling(r(n)/s(n)), where s(n) = 1 - r(1)/a(1) - r(2)/a(2) - ... - r(n-1)/a(n-1).

r(1)/a(1) + ... + r(n)/a(n) + ... = 1

Example

a(1) = ceiling(r(1)) = ceiling(1/tau) = ceiling(0.618...) = 1;
a(2) = ceiling(r(2)/(1 - r(1)/1) = 3;
a(3) = ceiling(r(3)/(1 - r(1)/1 - r(2)/2) = 6.
The first 6 terms of the series r(1)/a(1) + ... + r(n)/a(n) + ...  are
0.618..., 0.872..., 0.990..., 0.975..., 0.999..., 0.99999999959...

Mathematica

$MaxExtraPrecision = Infinity; z = 13;
r[k_] := N[k/GoldenRatio^k, 1000]; f[x_, 0] = x;
n[x_, k_] := n[x, k] = Ceiling[r[k]/f[x, k - 1]]
f[x_, k_] := f[x, k] = f[x, k - 1] - r[k]/n[x, k]
x = 1; Table[n[x, k], {k, 1, z}]
N[Sum[r[k]/n[x, k], {k, 1, 13}], 200]

Crossrefs

Cf. A001620, A270744, A094214.

Sequence in context: A215492 A125817 A053948 * A137091 A137135 A069077

Adjacent sequences: A270742 A270743 A270744 * A270746 A270747 A270748

Keyword

nonn,easy

Author

Clark Kimberling, Apr 09 2016

Status

approved