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A080041 a(n)=floor((1+sqrt(3))^n). 1
1, 2, 7, 20, 55, 152, 415, 1136, 3103, 8480, 23167, 63296, 172927, 472448, 1290751, 3526400, 9634303, 26321408, 71911423, 196465664, 536754175, 1466439680, 4006387711, 10945654784, 29904084991, 81699479552, 223207129087 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(n)=A080040(n)-(1+(-1)^n)/2

LINKS

Table of n, a(n) for n=0..26.

Index entries for linear recurrences with constant coefficients, signature (2,3,-2,-2).

FORMULA

G.f.: g(t)=(1+2t^3)/( (t-1)*(1+t)*(2*t^2+2*t-1)).

MATHEMATICA

CoefficientList[Series[(1+2t^3)/(1-2t-3t^2+2t^3+2t^4), {t, 0, 30}], t]

Floor[(1+Sqrt[3])^Range[0, 30]] (* Harvey P. Dale, Sep 14 2012 *)

CROSSREFS

Sequence in context: A035508 A018033 A000149 * A049681 A027120 A094982

Adjacent sequences:  A080038 A080039 A080040 * A080042 A080043 A080044

KEYWORD

easy,nonn

AUTHOR

Mario Catalani (mario.catalani(AT)unito.it), Jan 21 2003

STATUS

approved

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Last modified October 18 14:45 EDT 2018. Contains 316322 sequences. (Running on oeis4.)