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 A028259 Engel expansion of the golden ratio, (1 + sqrt(5))/2 = 1.61803... . 5

%I

%S 1,2,5,6,13,16,16,38,48,58,104,177,263,332,389,4102,4575,5081,9962,

%T 18316,86613,233239,342534,964372,1452850,7037119,7339713,8270361,

%U 12855437,15900982,19211148,1365302354,1565752087,1731612283

%N Engel expansion of the golden ratio, (1 + sqrt(5))/2 = 1.61803... .

%C Cf. A006784 for definition of Engel expansion.

%C (sqrt(5) - 1)/2 = 1/(golden ratio) has the same Engel expansion starting with a(2). - _G. C. Greubel_, Oct 16 2016

%C Each Engel expansion for a constant x (x > 0) starts with floor(x) 1's. After that, the mean growth of the terms is by a factor e for most constants x, i.e., the order of magnitude of the n-th entry is exp(n-floor(c)), for n large enough. This comment is similar to the fact that for the continued fraction terms of most constants, the geometric mean of those terms equals the Khintchine constant for n large enough. Moreover, note that for the golden section, all continued fraction terms are 1 and thus do not obey the Gauss-Kuzmin distribution which leads to the Khintchine constant (i.e., the Khintchine measure for the golden ratio is 1), but the Engel expansion does obey the statistic behavior for most constants. - _A.H.M. Smeets_, Aug 24 2018

%D F. Engel, Entwicklung der Zahlen nach Stammbruechen, Verhandlungen der 52. Versammlung deutscher Philologen und Schulmaenner in Marburg, 1913, pp. 190-191.

%H A.H.M. Smeets, <a href="/A028259/b028259.txt">Table of n, a(n) for n = 1..2406</a> (Terms 1 through 300 from T. D. Noe, 301 through 698 from Simon Plouffe, and 699 through 1500 from G. C. Greubel)

%H F. Engel, <a href="/A006784/a006784.pdf">Entwicklung der Zahlen nach Stammbruechen</a>, Verhandlungen der 52. Versammlung deutscher Philologen und Schulmaenner in Marburg, 1913, pp. 190-191. English translation by Georg Fischer, included with his permission.

%H P. Erdős and Jeffrey Shallit, <a href="http://www.numdam.org/item?id=JTNB_1991__3_1_43_0">New bounds on the length of finite Pierce and Engel series</a>, Sém. Théor. Nombres Bordeaux (2) 3 (1991), no. 1, 43-53.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/EngelExpansion.html">Engel Expansion</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GoldenRatio.html">Golden Ratio</a>

%H <a href="/index/El#Engel">Index entries for sequences related to Engel expansions</a>

%F Lim_{n -> oo} log(a(n + floor(golden ratio)))/n = 1.

%t EngelExp[ A_, n_ ] := Join[ Array[ 1&, Floor[ A ] ], First@Transpose@NestList[ {Ceiling[ 1/Expand[ #[ [ 1 ] ]#[ [ 2 ] ]-1 ] ], Expand[ #[ [ 1 ] ]#[ [ 2 ] ]-1 ]}&, {Ceiling[ 1/(A-Floor[ A ]) ], A-Floor[ A ]}, n-1 ] ]

%o (Python)

%o j = 0

%o while j<3100000:

%o # to obtain n correct Engel expansion terms about n^2/2 continued fraction steps are needed; 3100000 is a safe bound

%o ....if j == 0:

%o ........p0,q0 = 1,1

%o ....elif j == 1:

%o ........p1,q1 = p0+1,1

%o ....else:

%o ........p0,p1 = p1,p1+p0

%o ........q0,q1 = q1,q1+q0

%o ....j = j+1

%o i = 0

%o while i < 2410:

%o ....i = i+1

%o ....a = q0//p0+1

%o ....print(i,a)

%o ....p0 = a*p0-q0

%o # _A.H.M. Smeets_, Aug 24 2018

%Y Cf. A001622, A220398.

%K nonn,easy,nice

%O 1,2

%A Naoki Sato (naoki(AT)math.toronto.edu), Dec 11 1999

%E Corrected and extended by _Vladeta Jovovic_, Aug 16 2001

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Last modified April 5 06:13 EDT 2020. Contains 333238 sequences. (Running on oeis4.)