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A133666 a(n) = a(n-1) - 16*a(n-2), a(0)=1, a(1)=4. 1
1, 4, -12, -76, 116, 1332, -524, -21836, -13452, 335924, 551156, -4823628, -13642124, 63535924, 281809908, -734764876, -5243723404, 6512514612, 90412089076, -13788144716, -1460381569932, -1239771254476, 22126333864436, 41962673936052 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..23.

FORMULA

G.f.: (1+3*x) / (1-x+16*x^2).

a(n) = Sum_{k=0..n} A133607(n,k)*4^k. - Philippe Deléham, Dec 29 2007

a(n) = -(1/6)*i*sqrt(7)*(1/2 + (3/2)*i*sqrt(7))^n + (1/6)*i*sqrt(7)*(1/2 - (3/2)*i*sqrt(7))^n + (1/2)*(1/2 - (3/2)*i*sqrt(7))^n + (1/2)*(1/2 + (3/2)*i*sqrt(7))^n, with n >= 0 and i=sqrt(-1). - Paolo P. Lava, Nov 18 2008

CROSSREFS

Sequence in context: A190340 A232325 A291487 * A318432 A078628 A301340

Adjacent sequences:  A133663 A133664 A133665 * A133667 A133668 A133669

KEYWORD

easy,sign

AUTHOR

Philippe Deléham, Dec 28 2007, corrected Jan 04 2008

EXTENSIONS

a(19) corrected and more terms from Sean A. Irvine, May 19 2019

STATUS

approved

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Last modified August 14 13:57 EDT 2020. Contains 336481 sequences. (Running on oeis4.)