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A005229
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a(1)=a(2)=1; for n>2, a(n)=a(a(n-2))+a(n-a(n-2)).
(Formerly M0441)
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30
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1, 1, 2, 3, 3, 4, 5, 6, 6, 7, 7, 8, 9, 10, 10, 11, 12, 12, 13, 14, 15, 16, 16, 17, 17, 18, 19, 19, 20, 20, 21, 22, 23, 24, 24, 25, 26, 26, 27, 28, 29, 29, 30, 30, 30, 31, 32, 33, 34, 35, 36, 36, 37, 37, 38, 39, 39, 40, 41, 42, 43, 43, 44, 45, 45, 45, 46
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| By induction a(n)<=n, but exact rate of growth is not known.
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REFERENCES
| J. Arkin, D. C. Arney, L. S. Dewald and W. E. Ebel, Jr., Families of recursive sequences, J. Rec. Math., 22 (No. 22, 1990), 85-94.
C. L. Mallows, Conway's challenge sequence, Amer. Math. Monthly, 98 (1991), 5-20.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
Nick Hobson, Python program for this sequence
N. J. A. Sloane, My favorite integer sequences, in Sequences and their Applications (Proceedings of SETA '98).
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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MAPLE
| A005229 := proc(n) option remember; if n<=2 then 1 else A005229(A005229(n-2))+A005229(n-A005229(n-2)); fi; end;
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PROG
| (PARI) a(n)=an[ n ]; an=vector(100, n, 1); for(n=3, 100, an[ n ]=a(a(n-2))+a(n-a(n-2)))
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CROSSREFS
| Cf. A004001, A051105.
Sequence in context: A006161 A132351 A025556 * A091245 A100618 A061288
Adjacent sequences: A005226 A005227 A005228 * A005230 A005231 A005232
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KEYWORD
| nonn,nice,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)
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EXTENSIONS
| Typo in definition corrected by Nick Hobson, Feb 21 2007
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