A270138 - OEIS

A270138

Continued fraction expansion of the constant 6/A270121(1)+Sum_{n>=2}1/A270121(n).

0, 1, 6, 2, 7, 32, 112, 10800, 403200, 17418254400, 1755760043520000

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OFFSET

0,3

COMMENTS

A270121 is defined by the following recurrence: if A270121(n)=x(n) then x(n+1)*x(n-1)=x(n)^2*(1+n*x(n)) for n>=1, with x(1)=7, x(2)=112; and for A270124, if A270124(n)=y(n) then y(0)=2 and y(n)=x(n+1)/x(n) for n>=1. Both of these sequences appear in this continued fraction expansion, which defines a transcendental number.

LINKS

Table of n, a(n) for n=0..10.

A. N. W. Hone, Curious continued fractions, nonlinear recurrences and transcendental numbers, Journal of Integer Sequences, Vol. 18 (2015), Article 15.8.4.

A. N. W. Hone, Continued fractions for some transcendental numbers, arXiv:1509.05019 [math.NT], 2015-2016, Monatsh. Math. DOI: 10.1007/s00605-015-0844-2.

FORMULA

a(2*n+1) = n*A270124(n-1), a(2*n+2) = A270121(n) for n>=1.

EXAMPLE

6/A270121(1)+Sum_{n>=2}1/A270121(n)=6/7+1/112+1/403200+1/1755760043520000+...

=[0;1,6,2,7,32,112,10800,403200,17418254400,...]

=[0;1,6,A270124(0),A270121(1),2*A270124(1),A270121(2),3*A270124(2),A270121(3),4*A270124(3),...] (continued fraction).

CROSSREFS

Cf. A112373, A114550, A114551, A114552.

Sequence in context: A307086 A021090 A368669 * A177889 A086744 A242301

Adjacent sequences: A270135 A270136 A270137 * A270139 A270140 A270141

KEYWORD

nonn,cofr

AUTHOR

Andrew Hone, Mar 11 2016

STATUS

approved