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Search: id:A107390
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| A107390 |
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Composite Fibonacci sequence: each term is the composite with index equal to the sum of the previous two terms. |
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1
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| 4, 6, 18, 36, 76, 147, 285, 532, 984, 1795, 3237, 5793, 10293, 18168, 31887, 55709, 96926, 167972, 290136, 499615, 857947, 1469576, 2511369, 4282663, 7289002, 12383250, 21002336, 35564859, 60136917, 101547211, 171253466, 288461204
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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What is the value of lim(n -> infinity) a(n)/a(n+1)? - Ryan Propper (rpropper(AT)stanford.edu), Jan 11 2007
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FORMULA
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a(n) = composite(a(n-1)+a(n-2)); a(1)=4; a(2)=6;
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EXAMPLE
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a(5)=composite(18+36)=composite(54)=76
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MATHEMATICA
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Composite[n_Integer] := FixedPoint[n + PrimePi[ # ] + 1 &, n + PrimePi[n] + 1]; a = 4; b = 6; Do[c = Composite[a + b]; Print[c]; a = b; b = c, {n, 100}] - Ryan Propper (rpropper(AT)stanford.edu), Jan 11 2007
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CROSSREFS
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Cf. A002808, A000045, A107327.
Sequence in context: A138276 A088810 A005199 this_sequence A051253 A064403 A060667
Adjacent sequences: A107387 A107388 A107389 this_sequence A107391 A107392 A107393
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KEYWORD
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nonn,easy
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AUTHOR
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Christopher M. Tomaszewski (cmt1288(AT)comcast.net), May 24 2005
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EXTENSIONS
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More terms from Ryan Propper (rpropper(AT)stanford.edu), Jan 11 2007
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