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A057819 a(0)=4, a(1)=9, a(n)=4a(n-1)-a(n-2). 0
4, 9, 32, 119, 444, 1657, 6184, 23079, 86132, 321449, 1199664, 4477207, 16709164, 62359449, 232728632, 868555079, 3241491684, 12097411657, 45148154944, 168495208119, 628832677532, 2346835502009, 8758509330504, 32687201820007 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

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

Tanya Khovanova, Recursive Sequences

Index entries for linear recurrences with constant coefficients, signature (4,-1).

FORMULA

G.f.: (4-7x)/(1-4x+x^2). [From Philippe Deléham, Nov 16 2008]

a(n)=-(1/6)*sqrt(3)*[2-sqrt(3)]^n+(1/6)*sqrt(3)*[2+sqrt(3)]^n+2*[2-sqrt(3)]^n+2*[2 +sqrt(3)]^n, with n>=0 [From Paolo P. Lava, Nov 20 2008]

MATHEMATICA

Transpose[NestList[{Last[#], 4Last[#]-First[#]}&, {4, 9}, 40]][[1]]  (* Harvey P. Dale, Mar 09 2011 *)

CROSSREFS

Sequence in context: A149119 A149120 A219151 * A129196 A119574 A006393

Adjacent sequences:  A057816 A057817 A057818 * A057820 A057821 A057822

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Nov 09 2000

STATUS

approved

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Last modified November 18 12:21 EST 2017. Contains 294891 sequences.