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Search: id:A087206
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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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+0
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; listen)
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OFFSET
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0,2
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COMMENT
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Binomial transform of A056487. Unsigned version of A152174.
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FORMULA
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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]
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CROSSREFS
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Cf. A060925.
Equals (1/2) * A063727(n-1). Cf. A006483.
Sequence in context: A126986 A090576 A152174 this_sequence A081875 A102433 A100320
Adjacent sequences: A087203 A087204 A087205 this_sequence A087207 A087208 A087209
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Aug 25 2003
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EXTENSIONS
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Corrected comment. - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Nov 27 2008
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