login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A215712 Numerator of sum(i=1..n, 3*i/4^i ) 2
3, 9, 81, 21, 1359, 2727, 21837, 21843, 349515, 699045, 5592393, 2796201, 89478471, 178956963, 1431655749, 1431655761, 22906492227, 45812984481, 366503875905, 22906492245, 5864062014783, 11728124029599, 93824992236861, 93824992236879, 1501199875790139 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The limit as n goes to infinity is 4/3.
REFERENCES
Calvin C. Clawson, The Beauty and Magic of Numbers. New York: Plenum Press (1996): 96.
LINKS
EXAMPLE
a(4) = 21 because 3/4 + 6/16 + 9/64 + 12/256 = 3/4 + 3/8 + 9/64 + 3/64 = 48/64 + 24/64 + 9/64 + 3/64 = 84/64 = 21/16.
MATHEMATICA
Table[Numerator[Sum[3i/4^i, {i, n}]], {n, 40}]
PROG
(Magma) [Numerator(&+[3*i/4^i: i in [1..n]]): n in [1..25]]; // Bruno Berselli, Sep 03 2012
CROSSREFS
Cf. A215713 for the denominators.
A036295/A036296 is the same with i/2^i instead of 3i/4^i.
Cf. A122553.
Sequence in context: A032330 A018604 A301535 * A000218 A139731 A259986
KEYWORD
nonn,easy,frac
AUTHOR
Alonso del Arte, Aug 21 2012
EXTENSIONS
a(17) corrected by Vincenzo Librandi, Sep 04 2012
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 06:57 EDT 2024. Contains 371265 sequences. (Running on oeis4.)