The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
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!)
A029745 Expansion of (1 + 2x + 6x^2 + x^3)/(1 - 2x^2). 1
1, 2, 8, 5, 16, 10, 32, 20, 64, 40, 128, 80, 256, 160, 512, 320, 1024, 640, 2048, 1280, 4096, 2560, 8192, 5120, 16384, 10240, 32768, 20480, 65536, 40960, 131072, 81920, 262144, 163840, 524288, 327680, 1048576, 655360, 2097152, 1310720, 4194304 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Note that 4 is the only power of 2 not here. All terms are either 2^k or 5*2^k.
LINKS
FORMULA
G.f.: (1 + 2x + 6x^2 + x^3)/(1 - 2x^2).
Sum_{n>=1} 1/a(n) = 43/20. - Amiram Eldar, Jan 21 2022
MATHEMATICA
LinearRecurrence[{0, 2}, {1, 2, 8, 5}, 50] (* or *) With[{nn=20}, Join[{1, 2}, Riffle[ 8*2^Range[0, nn], 5 2^Range[0, nn]]]] (* Harvey P. Dale, Sep 28 2016 *)
PROG
(PARI) a(n)=if(n<2, 1+max(-1, n), 2^(n\2)*if(n%2, 5/2, 4))
CROSSREFS
Cf. A094958 (numbers of the form 2^k or 5*2^k).
Sequence in context: A309792 A318725 A155901 * A332067 A183232 A344691
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Edited by T. D. Noe, Nov 12 2010
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 June 17 18:36 EDT 2024. Contains 373463 sequences. (Running on oeis4.)