login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A128415 Expansion of (1-4x^2)/(1+3x+4x^2). 3
1, -3, 1, 9, -31, 57, -47, -87, 449, -999, 1201, 393, -5983, 16377, -25199, 10089, 70529, -251943, 473713, -413367, -654751, 3617721, -8234159, 10231593, 2241857, -47651943, 133988401, -211357431, 98118689 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Row sums of number triangle A128414.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (-3,-4).

FORMULA

For n>0, a(n) = (1/r)^n + (1/s)^n, with r = (-3-i*sqrt(7))/8 and s = (-3+i*sqrt(7))/8 the roots of 4x^2+3x+1. - Ralf Stephan, Jul 20 2013

a(n) = -3*a(n-1) - 4*a(n-2) for n > 2. - Harry Richman, May 05 2020

MATHEMATICA

CoefficientList[Series[(1 - 4 x^2) / (1 + 3 x + 4 x^2), {x, 0, 40}], x] (* Vincenzo Librandi, Jul 20 2013 *)

CROSSREFS

Sequence in context: A273464 A105951 A038202 * A227795 A090479 A227758

Adjacent sequences:  A128412 A128413 A128414 * A128416 A128417 A128418

KEYWORD

easy,sign

AUTHOR

Paul Barry, Mar 02 2007

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 5 09:47 EST 2020. Contains 338945 sequences. (Running on oeis4.)