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Search: id:A001856
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| A001856 |
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A self-generating sequence: every positive integer occurs as a(i)-a(j) for a unique pair i,j.
(Formerly M1112 N0425)
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+0
2
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| 1, 2, 4, 8, 16, 21, 42, 51, 102, 112, 224, 235, 470, 486, 972, 990, 1980, 2002, 4004, 4027, 8054, 8078, 16156, 16181, 32362, 32389, 64778, 64806, 129612, 129641, 259282, 259313, 518626, 518658, 1037316, 1037349, 2074698, 2074734, 4149468
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
R. L. Graham, Problem E1910, Amer. Math. Monthly, 73 (1966), 775.
R. K. Guy, The second strong law of small numbers. Math. Mag. 63 (1990), no. 1, 3-20.
R. K. Guy, Unsolved Problems in Number Theory, E25.
M. Hall, Cyclic projective planes, Duke Math. J., 4 (1947), 1079-1090.
C. B. A. Peck, Remark on Problem E1910, Amer. Math. Monthly, 75 (1968), 80-81.
W. Sierpi\'{n}ski, Elementary Theory of Numbers. Pa\'{n}st. Wydaw. Nauk., Warsaw, 1964, p. 444.
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LINKS
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W. Sierpi\'{n}ski, Elementary Theory of Numbers, Warszawa 1964.
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FORMULA
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a(1)=1, a(2)=2, a(2n+1)=2a(2n), a(2n+2)=a(2n+1)+r(n), where r(n) = smallest positive number not of form a(j)-a(i) with 1<=i<j<=2n+1.
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CROSSREFS
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Cf. A054540.
Sequence in context: A134162 A045776 A102252 this_sequence A002081 A102039 A045844
Adjacent sequences: A001853 A001854 A001855 this_sequence A001857 A001858 A001859
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KEYWORD
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nonn,easy,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 Larry Reeves (larryr(AT)acm.org), Sep 14 2000
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