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

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A084241 a(n) = -5*a(n-1)-4*a(n-2) with n>1, a(0)=0, a(1)=1. 2
0, 1, -5, 21, -85, 341, -1365, 5461, -21845, 87381, -349525, 1398101, -5592405, 22369621, -89478485, 357913941, -1431655765, 5726623061, -22906492245, 91625968981, -366503875925, 1466015503701, -5864062014805, 23456248059221, -93824992236885 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

abs(a(n))=A002450(n)=A001045(2n).

Binomial transform is (0,1,-3,9,-27,...).

LINKS

Table of n, a(n) for n=0..24.

Index to sequences with linear recurrences with constant coefficients, signature (-5,-4).

FORMULA

a(n) = ((-1)^n-(-4)^n)/3.

a(n) = sum(k=1..n, (-1)^(n+k)*binomial(n, k)(-3)^(k-1)).

G.f.: x/((1+x)*(1+4*x)).

E.g.f.: (exp(-x)-exp(-4x))/3.

CROSSREFS

Apart from signs, identical to A002450.

Cf. A084240.

Sequence in context: A246986 A247001 A028948 * A002450 A187063 A026855

Adjacent sequences:  A084238 A084239 A084240 * A084242 A084243 A084244

KEYWORD

sign,easy

AUTHOR

Paul Barry, May 21 2003

STATUS

approved

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

Content is available under The OEIS End-User License Agreement .

Last modified November 24 02:09 EST 2014. Contains 249867 sequences.