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A155181 a(n)=5*a(n-1)+a(n-2), n>2 ; a(0)=1, a(1)=4, a(2)=20 . 1
1, 4, 20, 104, 540, 2804, 14560, 75604, 392580, 2038504, 10585100, 54964004, 285405120, 1481989604, 7695353140, 39958755304, 207489129660, 1077404403604, 5594511147680, 29049960142004, 150844311857700, 783271519430504 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..21.

FORMULA

G.f.: (1-x-x^2)/(1-5*x-x^2).

a(n)=2*{[(5/2)+(1/2)*sqrt(29)]^(n-1)+[(5/2)-(1/2)*sqrt(29)]^(n-1)}+(10/29)*sqrt(29)*{[(5/2)+(1/2)*sqrt(29)]^(n-1)-[(5/2)-(1/2)*sqrt(29)]^(n-1)}+[C(2*n,n) mod 2], with n>=0 [From Paolo P. Lava, Jan 26 2009]

a(n) = Sum_{k, 0<=k<=n} A155161(n,k)*4^k. - Philippe Deléham, Feb 08 2012

CROSSREFS

Sequence in context: A229135 A226198 A155485 * A082761 A076035 A120978

Adjacent sequences:  A155178 A155179 A155180 * A155182 A155183 A155184

KEYWORD

nonn,easy

AUTHOR

Philippe Deléham, Jan 21 2009

STATUS

approved

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Last modified October 18 22:26 EDT 2019. Contains 328211 sequences. (Running on oeis4.)