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Search: id:A121511
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| A121511 |
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a(n)= a(n-1) +a(n-4) -a(n-5) . |
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+0
1
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| 1, 5, 13, 25, 5, 9, 17, 29, 9, 13, 21, 33, 13, 17, 25, 37, 17, 21, 29, 41, 21, 25, 33, 45, 25, 29, 37, 49, 29, 33, 41, 53, 33, 37, 45, 57, 37, 41, 49, 61, 41, 45, 53, 65, 45, 49, 57, 69, 49, 53
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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This sequence gives a linearly increasing triangle shaped form on plotting.
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FORMULA
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G.f.: -x*(-1-4*x-8*x^2-12*x^3+21*x^4)/( (1+x)*(x^2+1)*(x-1)^2). [Oct 14 2009]
a(n) = n+17/2 +7*(-1)^n/2 + A057077(n+1)*A010720(n-1). [Oct 14 2009]
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MATHEMATICA
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M = {{0, 1, 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1}, {1, 0, 0, 0}} v[1] = {1, 5, 13, 25} v[n_] := v[n] = M.v[n - 1] + {0, 0, 0, 4} a = Table[v[n][[1]], {n, 1, 50}]
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CROSSREFS
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Cf. A001844.
Sequence in context: A119248 A114998 A140090 this_sequence A156679 A004627 A066782
Adjacent sequences: A121508 A121509 A121510 this_sequence A121512 A121513 A121514
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KEYWORD
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nonn,easy
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AUTHOR
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Roger Bagula (rlbagulatftn(AT)yahoo.com), Sep 07 2006
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EXTENSIONS
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Definition replaced by recurrence - The Assoc. Editors of the OEIS, Oct 14 2009
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