login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A073415 Denominator of the n-th convergent to Sum_{k>=0} 1/2^(2^k). 3
1, 1, 5, 11, 49, 207, 1291, 5371, 12033, 53503, 333051, 719605, 3211471, 19988431, 83165195, 352649211, 788463617, 3506503679, 21827485691, 47161475061, 210473385935, 889055018801, 5544803498741, 23068269013765, 51681341526271 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Robert Israel, Table of n, a(n) for n = 1..1650

FORMULA

a(n) = a(n-1) A007400(n) + a(n-2). - Robert Israel, Jun 14 2016

MAPLE

a007400:= proc(n) option remember; local n8, n16;

    n8:= n mod 8;

    if n8 = 0 or n8 = 3 then return 2

    elif n8 = 4 or n8 = 7 then return 4

    elif n8 = 1 then return procname((n+1)/2)

    elif n8 = 2 then return procname((n+2)/2)

    fi;

    n16:= n mod 16;

    if n16 = 5 or n16 = 14 then return 4

    elif n16 = 6 or n16 = 13 then return 6

    fi

end proc:

a007400(0):= 0: a007400(1):= 1: a007400(2):= 4:

A[1]:= 1: A[2]:= 1:

for n from 3 to 100 do

  A[n]:= A[n-1]*a007400(n-1)+A[n-2];

od:

seq(A[n], n=1..100); # Robert Israel, Jun 14 2016

PROG

(PARI) a(n)=component(component(contfracpnqn(contfrac(sum(k=0, 20, 1/2^(2^k)), n)), 1), 2)

CROSSREFS

Cf. A007400, A007404, A073414.

Sequence in context: A149518 A149519 A149520 * A176832 A289284 A149521

Adjacent sequences:  A073412 A073413 A073414 * A073416 A073417 A073418

KEYWORD

easy,frac,nonn

AUTHOR

Benoit Cloitre, Aug 23 2002

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 16 20:35 EDT 2019. Contains 328103 sequences. (Running on oeis4.)