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A087206
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a(n)=2a(n-1)+4a(n-2),a(0)=1,a(1)=4.
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5
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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, 2036636581888
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Binomial transform of A056487. Unsigned version of A152174.
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FORMULA
| G.f.: (1+2x)/(1-2x-4x^2); a(n)=(1-sqrt(5))^n(1/2-3sqrt(5)/10)+(1+sqrt(5))^n(1/2+3sqrt(5/10)).
a(n)=2^nFib(n+2). - Paul Barry (pbarry(AT)wit.ie), Mar 22 2004
a(n)=((1+sqrt5)^n-(1-sqrt5)^n)/sqrt80. Offset 2. a(4)=12. [From Al Hakanson (hawkuu(AT)gmail.com), Apr 11 2009]
G.f.: 1/(-2x-1/(-2x-1)). [From Paul Barry (pbarry(AT)wit.ie), Mar 24 2010]
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CROSSREFS
| Cf. A060925.
Equals (1/2) * A063727(n-1). Cf. A006483.
Sequence in context: A126986 A090576 A152174 * A081875 A102433 A100320
Adjacent sequences: A087203 A087204 A087205 * A087207 A087208 A087209
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Aug 25 2003
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EXTENSIONS
| Corrected comment. - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Nov 27 2008
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