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A270548 Denominators of r-Egyptian fraction expansion for sqrt(2) - 1, where r(k) = 1/(2k-1). 1
3, 5, 15, 163, 29203, 1370794960, 5693192315226228214, 247405800822801380465687897681838336769, 267682228701778523205506744045084667800917057557706608910309126004853790212423 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
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.
LINKS
Eric Weisstein's World of Mathematics, Egyptian Fraction
EXAMPLE
sqrt(2) - 1 = 1/(1*3) + 1/(3*5) + 1/(5*15) + 1/(7*163) + ...
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 = Sqrt(2) - 1; Table[n[x, k], {k, 1, z}]
PROG
(PARI) r(k) = 1/(2*k-1);
f(k, x) = if (k==0, x, f(k-1, x) - r(k)/a(k, x); );
a(k, x=sqrt(2)-1) = ceil(r(k)/f(k-1, x)); \\ Michel Marcus, Apr 03 2016
CROSSREFS
Sequence in context: A307999 A018771 A214534 * A292339 A175138 A248795
KEYWORD
nonn,frac,easy
AUTHOR
Clark Kimberling, Apr 02 2016
STATUS
approved

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Last modified April 17 10:33 EDT 2024. Contains 371763 sequences. (Running on oeis4.)