A270580 Denominators of r-Egyptian fraction expansion for sqrt(1/2), where r(k) = 1/(k+1).

1, 2, 7, 43, 2233, 5100361, 40162526999265, 25631935256046376027999327548, 973579151885397220180400699680033378225854987721289580493, 20355636044566797478491707686529410726939762602606154042023303177125252037523393842033572704449460687246942494130101

Offset

1,2

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..12

Eric Weisstein's World of Mathematics, Egyptian Fraction

Index entries for sequences related to Egyptian fractions

Example

sqrt(1/2) = 1/(2*1) + 1/(3*2) + 1/(4*7) + 1/(5*43) + ...

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 = Sqrt[1/2]; Table[n[x, k], {k, 1, z}]

Crossrefs

Cf. A269993.

Sequence in context: A198946 A212270 A270348 * A103084 A041507 A158107

Adjacent sequences: A270577 A270578 A270579 * A270581 A270582 A270583

Keyword

nonn,frac,easy

Author

Clark Kimberling, Apr 03 2016

Status

approved