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A003065 Number of integers with a shortest addition chain of length n.
(Formerly M0707)
7
1, 1, 2, 3, 5, 9, 15, 26, 44, 78, 136, 246, 432, 772, 1382, 2481, 4490, 8170, 14866, 27128, 49544, 90371, 165432, 303475, 558275, 1028508, 1896704, 3501029, 6465774, 11947258, 22087489, 40886910, 75763102, 140588339 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, Vol. 2, p. 459.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

See A003313 for a much more extensive list of references and links.

LINKS

R. J. Mathar, Table of n, a(n) for n = 0..38

Daniel Bleichenbacher, Efficiency and Security of Cryptosystems based on Number Theory, PhD Thesis, Diss. ETH No. 11404, Z├╝rich 1996. See p. 61.

M. Elia and F. Neri, A note on addition chains and some related conjectures, pp. 166-181 of R. M. Capocelli, ed., Sequences, Springer-Verlag, NY 1990.

Achim Flammenkamp, Shortest addition chains

Index to sequences related to the complexity of n

EXAMPLE

a(6) = 15 because 15 numbers have shortest addition chains involving 6 additions. These numbers are 19,21,22,23,25,26,27,28,30,33,34,36,40,48,64.

CROSSREFS

Cf. A003064, A003313.

Cf. A114623 [Number of integers for which Knuth's power tree method produces an addition chain of length n].

Sequence in context: A286887 A018157 A228644 * A239909 A185648 A228645

Adjacent sequences:  A003062 A003063 A003064 * A003066 A003067 A003068

KEYWORD

nonn,nice,hard

AUTHOR

N. J. A. Sloane, Don Knuth

EXTENSIONS

Updated through a(28) from Achim Flammenkamp's web site Feb 01 2005

a(28) corrected from 6465773 to 6465774, based on information received from Neill M. Clift. - Hugo Pfoertner, Jan 29 2006

a(29)-a(30) from Neill M. Clift, Jun 15 2007

a(31)-a(33) from Neill M. Clift, May 21 2008

b-file up to a(38) extracted from Achim Flammenkamp's web site. R. J. Mathar, May 14 2013

STATUS

approved

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Last modified June 14 14:21 EDT 2021. Contains 345025 sequences. (Running on oeis4.)