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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A168420 a(n) = 4 + 10*floor(n/2). 1
4, 14, 14, 24, 24, 34, 34, 44, 44, 54, 54, 64, 64, 74, 74, 84, 84, 94, 94, 104, 104, 114, 114, 124, 124, 134, 134, 144, 144, 154, 154, 164, 164, 174, 174, 184, 184, 194, 194, 204, 204, 214, 214, 224, 224, 234, 234, 244, 244, 254, 254, 264, 264, 274, 274, 284 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

a(n) = 10*n - a(n-1) - 2, with n>1, a(1)=4.

a(n) = (3 + 5*(-1)^n + 10*n)/2. - Paolo P. Lava, Nov 27 2009

G.f.: 2*x*(2 + 5*x - 2*x^2)/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 19 2013

a(n) = a(n-1) +a(n-2) -a(n-3). - Vincenzo Librandi, Sep 19 2013

a(n) = 2*A168278(n). - Bruno Berselli, Sep 19 2013

E.g.f.: (1/2)*(5 - 8*exp(x) + (10*x + 3)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 22 2016

MATHEMATICA

Table[4 + 10 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[(4 + 10 x - 4 x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 19 2013 *)

PROG

(MAGMA) [4+10*Floor(n/2): n in [1..70]]; // Vincenzo Librandi, Sep 19 2013

CROSSREFS

Cf. A017317, A168278.

Sequence in context: A098363 A276703 A170847 * A189814 A200553 A229392

Adjacent sequences:  A168417 A168418 A168419 * A168421 A168422 A168423

KEYWORD

nonn,easy,less

AUTHOR

Vincenzo Librandi, Nov 25 2009

EXTENSIONS

New definition by Vincenzo Librandi, Sep 19 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 | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified August 21 22:08 EDT 2017. Contains 290913 sequences.