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A128415 Expansion of (1-4x^2)/(1+3x+4x^2). 2
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 to sequences with 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

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: A225118 A105951 A038202 * A227795 A090479 A227758

Adjacent sequences:  A128412 A128413 A128414 * A128416 A128417 A128418

KEYWORD

easy,sign

AUTHOR

Paul Barry, Mar 02 2007

STATUS

approved

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Last modified April 16 18:26 EDT 2014. Contains 240626 sequences.