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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.
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: A063743 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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njas
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EXTENSIONS
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More terms from Jud McCranie (j.mccranie(AT)comcast.net)
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