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Search: id:A013989
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| A013989 |
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a(n) = (n+1)( a(n-1)/n + a(n-2) ). |
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+0
4
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| 1, 2, 6, 16, 50, 156, 532, 1856, 6876, 26200, 104456, 428352, 1821976, 7959056, 35857200, 165592576, 785514512, 3812387616, 18948962656, 96194028800, 498931946016, 2638959243712, 14234346694976
(list; graph; listen)
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OFFSET
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0,2
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REFERENCES
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rec.puzzles Dec 10 1995
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FORMULA
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E.g.f: x*exp(x*(x/2+1)) - Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 28 2005
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MAPLE
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A013989 := proc(n) option remember; if n <=1 then n+1; else (n+1)*(A013989(n-1)/n+A013989(n-2)); fi; end;
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CROSSREFS
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a(n) = A000085(n) * (n+1).
Cf. A000085.
Adjacent sequences: A013986 A013987 A013988 this_sequence A013990 A013991 A013992
Sequence in context: A052890 A052814 A000136 this_sequence A002841 A136509 A100664
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KEYWORD
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nonn,easy
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AUTHOR
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njas, Dan Hoey (Hoey(AT)AIC.NRL.Navy.Mil)
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