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A083671
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Array read by rows in which each row describes in words the composition of the previous row.
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1
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1, 1, 1, 2, 1, 1, 1, 1, 2, 3, 1, 1, 2, 2, 1, 1, 2, 1, 3, 3, 1, 2, 2, 1, 3, 2, 1, 2, 2, 2, 3, 1, 1, 4, 2, 1, 3, 3, 1, 1, 2, 1, 3, 1, 4, 4, 1, 1, 2, 2, 3, 1, 4, 3, 1, 2, 2, 1, 3, 2, 4, 2, 1, 3, 2, 2, 3, 1, 4, 2, 1, 3, 2, 2, 3, 1, 4, 2, 1, 3, 2, 2, 3, 1, 4, 2, 1, 3, 2, 2, 3, 1, 4, 2, 1, 3, 2, 2, 3, 1, 4, 2, 1, 3, 2, 2, 3, 1, 4, 2, 1, 3, 2, 2, 3, 1, 4
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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FORMULA
| Becomes periodic at row 13.
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EXAMPLE
| Array begins:
1
1 1
2 1
1 1 1 2
3 1 1 2
2 1 1 2 1 3
Explanation: look at 3 1 1 2. What do you see? Two 1's, one 2 and one 3, so the next row is 2 1 1 2 1 3.
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MATHEMATICA
| NestList[Function[test, Flatten[{Count[test, # ], # } & /@ Union[test]]], {1}, 13]
RunLengthEncode[x_List ] := (Through[ { Length, First}[ #1 ] ] &) /@ Split[ Sort[ x ]]; LookAndSay[ n_, d_:1 ] := NestList[ Flatten[ RunLengthEncode[ # ] ] &, {d}, n - 1 ]; F[n_] := LookAndSay[ n, 1 ][[ n ]]; Flatten[ Table[ F[n], {n, 18}]] (from Robert G. Wilson v Jan 22 2004)
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CROSSREFS
| Similar to A005151. Cf. A005150, A034002, A034003.
Sequence in context: A026791 A080576 A194673 * A201913 A029384 A094102
Adjacent sequences: A083668 A083669 A083670 * A083672 A083673 A083674
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KEYWORD
| nonn,tabf,easy,base
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), based on a query from Chasity Engle, Jan 20 2004
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EXTENSIONS
| More terms from Wouter Meeussen (wouter.meeussen(AT)pandora.be) and Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 22, 2004
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