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A113698
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Combinatorial sequence. Begin with 1 then 2 then 12 then 3 then all concatenations of all sizes of 1,2 and 3, then 4, then all concatenations of all sizes of 1,2,3,4 not included earlier etc.
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2
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1, 2, 12, 3, 13, 23, 123, 4, 14, 24, 34, 124, 134, 234, 1234, 5, 15, 25, 35, 45, 125, 135, 145, 235, 245, 345, 1235, 1245, 1345, 2345, 12345, 6, 16, 26, 36, 46, 56, 126, 136, 146, 156, 236, 246, 256, 346, 356, 456, 1236, 1246, 1256, 1346, 1356, 1456, 2346, 2356
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OFFSET
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1,2
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COMMENTS
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The index of n is 2^n for n<10. After 9 if n ( like 13, 23) has appeared earlier it will not appear but it will be used in the concatenation at its turn as mentioned above. needs better description.
The sequence contains groups of integers generated from seeds s=1,2,3,4,... A group is the sorted list of numbers defined by the seed and all concatenations of integers of previous groups with the seed, discarding any duplicates. - R. J. Mathar, Aug 31 2007
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LINKS
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T. D. Noe, Table of n, a(n) for n = 1..511
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EXAMPLE
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The group 4, 14, 24, 34, 124, 134, 234, 1234 is generated from the seed s=4 itself and attaching s=4 to the previous elements 1, 2, 12, 3, 13, 23, 123, that is 14, 24, 124, 34, 134, 234, 1234, then sorting within the group (moving 34 between 24 and 124).
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MATHEMATICA
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Flatten[Table[FromDigits /@ Complement[Subsets[Range[n]], Subsets[Range[n - 1]]], {n, 5}]] (* T. D. Noe, Feb 22 2012 *)
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CROSSREFS
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Cf. A113699.
Sequence in context: A012629 A082827 A072484 * A048794 A164869 A082292
Adjacent sequences: A113695 A113696 A113697 * A113699 A113700 A113701
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 11 2005
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EXTENSIONS
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More terms from R. J. Mathar, Aug 31 2007
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STATUS
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approved
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