A270585 Denominators of r-Egyptian fraction expansion for 1/Pi, where r(k) = 1/(k+1).

2, 5, 153, 21663, 647515546, 851446050371825387, 742303125094915071620208422217798950, 509982391580641403228264048782616183819262037197219855113797866110319327

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

Clark Kimberling, Table of n, a(n) for n = 1..11

Eric Weisstein's World of Mathematics, Egyptian Fraction

Index entries for sequences related to Egyptian fractions

Example

1/Pi = 1/(2*2) + 1/(3*5) + 1/(4*153) + 1/(5*21663) + ...

Mathematica

r[k_] := 1/(k+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/Pi; Table[n[x, k], {k, 1, z}]

Crossrefs

Cf. A269993.

Sequence in context: A307480 A062611 A263413 * A041505 A116629 A124275

Adjacent sequences: A270582 A270583 A270584 * A270586 A270587 A270588

Keyword

nonn,frac,easy

Author

Clark Kimberling, Apr 03 2016

Status

approved