A270557 Denominators of r-Egyptian fraction expansion for (1/2)^(1/3), where r(k) = 1/(2k-1).

2, 2, 2, 6, 35, 1828, 87102089, 9369260399911997, 79759690931475868535017424372273, 6278545782421133501164266118042557416295332543123744442037840298

Offset: 1

Author

Clark Kimberling, Apr 03 2016

Keywords

• nonn
• frac
• easy

Comments

Suppose that r is a sequence of rational numbers r(k) <= 1 for k >= 1, and that x is an irrational number in (0,1). Let f(0) = x, n(k) = floor(r(k)/f(k-1)), and f(k) = f(k-1) - r(k)/n(k). Then x = r(1)/n(1) + r(2)/n(2) + r(3)/n(3) + ..., the r-Egyptian fraction for x.

See A269993 for a guide to related sequences.

Examples

			(1/2)^(1/3) = 1/(1*2) + 1/(3*2) + 1/(5*2) + 1/(7*6) + ...
		

Links

• Clark Kimberling, Table of n, a(n) for n = 1..13
• Eric Weisstein's World of Mathematics, Egyptian Fraction
• Index entries for sequences related to Egyptian fractions

Crossrefs

Cf. A269993, A005408.

Programs

Mathematica

r[k_] := 1/(2k-1); f[x_, 0] = x; z = 10;
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 = (1/2)^(1/3); Table[n[x, k], {k, 1, z}]