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A152174
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a(n)=-2*a(n-1)+4*a(n-2), n>1 ; a(0)=1, a(1)=-4 .
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4
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1, -4, 12, -40, 128, -416, 1344, -4352, 14080, -45568, 147456, -477184, 1544192, -4997120, 16171008, -52330496, 169345024, -548012032, 1773404160, -5738856448, 18571329536, -60098084864, 194481487872, -629355315200
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Signed version of A087206.
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FORMULA
| G.f.: (1-2x)/(1+2x-4x^2). a(n)=Sum_{k, 0<=k<=n}A147703(n,k)*(-5)^k. a(n)=(-1)^n*A087206(n).
a(n)=(1/2)*{[ -1-sqrt(5)]^n+[ -1+sqrt(5)]^n+(3/10)*sqrt(5)*{[ -1-sqrt(5)]^n-[ -1+sqrt(5)]^n}, with n>=0 [From Paolo P. Lava (paoloplava(AT)gmail.com), Dec 01 2008]
<a href="/index/Rea#recLCC">Index to sequences with linear recurrences with constant coefficients</a>, signature (-2,4).
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PROG
| (PARI) Vec((1-2x)/(1+2x-4x^2)+O(x^99)) \\ Charles R Greathouse IV, Jan 11 2012
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CROSSREFS
| Sequence in context: A104525 A126986 A090576 * A087206 A081875 A102433
Adjacent sequences: A152171 A152172 A152173 * A152175 A152176 A152177
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KEYWORD
| sign,easy
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AUTHOR
| Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Nov 27 2008
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