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Search: id:A001857
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| A001857 |
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a(1)=2, a(2)=3; for n >= 3, a(n) is smallest number which is uniquely of the form a(j)+a(k) with 1<=j<k<n.
(Formerly M0634 N0231)
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+0
6
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| 2, 3, 5, 7, 8, 9, 13, 14, 18, 19, 24, 25, 29, 30, 35, 36, 40, 41, 46, 51, 56, 63, 68, 72, 73, 78, 79, 83, 84, 89, 94, 115, 117, 126, 153, 160, 165, 169, 170, 175, 176, 181, 186, 191, 212, 214, 230, 235, 240, 245, 266, 273, 278, 283, 288, 325, 331, 332, 337, 342
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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An Ulam-type sequence - see A002858 for many further references, comments, etc.
A plot of the first 10^6 terms shows a nearly straight line having a slope of about 11.1. In contrast to A002858, this sequence has many consecutive numbers; of the first 10^6 terms, consecutive numbers appear 141674 times! - T. D. Noe, Jan 21 2008
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REFERENCES
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S. R. Finch, Patterns in 1-additive sequences, Experimental Mathematics 1 (1992), 57-63.
S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 145-151.
R. K. Guy, Unsolved Problems in Number Theory, Section C4.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
S. M. Ulam, Problems in Modern Mathematics, Wiley, NY, 1960, p. ix.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
S. R. Finch, Ulam s-Additive Sequences
J. Cassaigne and S. R. Finch, A class of 1-additive sequences and additive recurrences
Experimental Mathematics, Home Page
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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CROSSREFS
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Cf. A100729.
Sequence in context: A144100 A086539 A049468 this_sequence A091532 A108345 A073629
Adjacent sequences: A001854 A001855 A001856 this_sequence A001858 A001859 A001860
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Jud McCranie (j.mccranie(AT)comcast.net)
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