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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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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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njas
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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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