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A121517
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a(n)=4*a(n-1)+4*a(n-2)-a(n-3); a(0)=1, a(1)=1, a(2)=7.
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0
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1, 1, 7, 31, 151, 721, 3457, 16561, 79351, 380191, 1821607, 8727841, 41817601, 200360161, 959983207, 4599555871, 22037796151, 105589424881, 505909328257, 2423957216401, 11613876753751, 55645426552351, 266613256008007
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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FORMULA
| a(n)=5*a(n-1)-a(n-2)+3*(-1)^n . g.f.: (1-3*x-x^2)/(1-4*x-4*x^2+x^3).
a(n)=(3/7)*(-1)^n+(2/7)*[5/2+(1/2)*sqrt(21)]^n+(2/7)*[5/2-(1/2)*sqrt(21)]^n, with n>=0 - Paolo P. Lava (paoloplava(AT)gmail.com), Jul 07 2008
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CROSSREFS
| Sequence in context: A005825 A086901 A003526 * A199216 A057620 A055625
Adjacent sequences: A121514 A121515 A121516 * A121518 A121519 A121520
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KEYWORD
| nonn
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AUTHOR
| Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Sep 08 2006
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