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Search: id:A037257
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| A037257 |
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a() = 1,3,... [ A037257 ], differences = 2,... [ A037258 ] and 2nd differences [ A037259 ] are disjoint and monotonic; adjoin next free number to 2nd differences unless it would produce a duplicate in which case ignore. |
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+0
8
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| 1, 3, 9, 20, 38, 64, 100, 148, 209, 284, 374, 480, 603, 745, 908, 1093, 1301, 1533, 1790, 2075, 2389, 2733, 3108, 3515, 3955, 4429, 4938, 5484, 6069, 6694, 7360, 8068, 8819, 9614, 10454, 11340, 12273, 13255, 14287, 15370, 16505, 17693, 18935, 20232
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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27 and 250 are the first two numbers to be ignored.
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REFERENCES
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I discovered this around 1979; Martin Gardner described a version of it in "Weird Numbers from Titan", Isaac Asimov's SF Magazine, May 1980, pp. 42ff.
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EXAMPLE
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After 1 3 9 20 with differences
------ 2 6 11 and 2nd differences
------- 4 5, the next free number is 7 so we get
----- 1 3 9 20 38 ...
------ 2 6 11 18 ...
------- 4 5 7 ....
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CROSSREFS
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Cf. A005228, A030124.
Sequence in context: A073716 A037048 A139142 this_sequence A145068 A027114 A145070
Adjacent sequences: A037254 A037255 A037256 this_sequence A037258 A037259 A037260
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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 25 2000
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