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Search: id:A133592
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| A133592 |
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a(n)=2*a(n-1)+6*a(n-2) for n>=3, a(0)=1, a(1)=2, a(2)=8 . |
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+0
2
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| 1, 2, 8, 28, 104, 376, 1376, 5008, 18272, 66592, 242816, 885184, 3227264, 11765632, 42894848, 156383488, 570136084, 2078573056, 7577962496, 27627363328, 100722501632, 367209183232, 1338753376256, 4880761851904, 17794043961344
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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G.f.: (1-2*x^2)/(1-2*x-6*x^2) . a(n) = Sum_{k, 0<=k<=n}A122950(n,k)*2^k .
a(n)=[1+sqrt(7)]^(n-1)+[1-sqrt(7)]^(n-1)-(3/7)*[1-sqrt(7)]^(n-1)*sqrt(7)+(3/7)*[1+sqrt(7)]^(n-1)*sqrt(7) +(1/3)*[C(2*n,n) mod 2], with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Nov 18 2008]
((7+2*sqrt(7))/21)*(1+sqrt(7))^n+((7-2*sqrt(7))/21)*(1-sqrt(7))^n for n=>1 [From Richard Choulet (richardchoulet(AT)yahoo.fr), Nov 19 2008]
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CROSSREFS
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Sequence in context: A104934 A056711 A114590 this_sequence A115967 A150714 A122447
Adjacent sequences: A133589 A133590 A133591 this_sequence A133593 A133594 A133595
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KEYWORD
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easy,nonn,new
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AUTHOR
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Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Dec 31 2007
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