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Search: id:A048776
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| 1, 4, 12, 32, 81, 200, 488, 1184, 2865, 6924, 16724, 40384, 97505, 235408, 568336, 1372096, 3312545, 7997204, 19306972, 46611168, 112529329, 271669848, 655869048
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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a(n)=2*a(n-1)+a(n-2) + n+1; a(0)=1, a(1)=4.
a(n) =(A000129(n+3)-(n+3))/2 =sum{j}[A047662[n-j+1, j+1] - Henry Bottomley (se16(AT)btinternet.com), Jul 09 2001
(1/2) [Pell(n+2) - n - 3 ], with Pell(n) = A000129(n). - Ralf Stephan, May 15 2007
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EXAMPLE
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a(n)=[ {(7/2 +(5/2)*sqrt(2))(1+sqrt(2))^n - (7/2-(5/2)*sqrt(2))(1-sqrt(2))^n}/2*sqrt(2) ]-(n+3)/2.
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MAPLE
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with(combinat):seq((fibonacci(n, 2)-n)/2, n=3..25); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 02 2008
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CROSSREFS
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Cf. A001333, A000129, A048739.
Sequence in context: A001787 A118442 A038592 this_sequence A135248 A120369 A001665
Adjacent sequences: A048773 A048774 A048775 this_sequence A048777 A048778 A048779
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KEYWORD
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easy,nonn
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AUTHOR
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Barry E. Williams
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