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!)
A168459 a(n) = (10*n + 5*(-1)^n - 3)/2. 3
1, 11, 11, 21, 21, 31, 31, 41, 41, 51, 51, 61, 61, 71, 71, 81, 81, 91, 91, 101, 101, 111, 111, 121, 121, 131, 131, 141, 141, 151, 151, 161, 161, 171, 171, 181, 181, 191, 191, 201, 201, 211, 211, 221, 221, 231, 231, 241, 241, 251, 251, 261, 261, 271, 271, 281 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = 10*n - a(n-1) - 8 with n>1, a(1)=1.
From Bruno Berselli, Sep 16 2013: (Start)
G.f.: x*(1 + 10*x - x^2)/((1+x)*(1-x)^2).
a(n) = A168457(n) - 1 = 2*A168282(n) - 1.
a(n) = a(n-1) +a(n-2) -a(n-3). (End)
a(n) = 1 + 10*floor(n/2). - Vincenzo Librandi, Sep 19 2013
E.g.f.: (1/2)*(5 - 2*exp(x) + (10*x - 3)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 23 2016
MATHEMATICA
Table[5 n + 5 (-1)^n/2 - 3/2, {n, 60}] (* Bruno Berselli, Sep 16 2013 *)
Table[1 + 10 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[(1 + 10 x - x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 19 2013 *)
PROG
(Magma) [1+10*Floor(n/2): n in [1..70]]; // Vincenzo Librandi, Sep 19 2013
CROSSREFS
Sequence in context: A003856 A167130 A299781 * A110414 A040111 A003887
KEYWORD
nonn,easy,less
AUTHOR
Vincenzo Librandi, Nov 26 2009
EXTENSIONS
New definition by Bruno Berselli, Sep 16 2013
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 April 15 11:37 EDT 2024. Contains 371681 sequences. (Running on oeis4.)