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Search: id:A141825
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| A141825 |
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Encodes permutations which "avoid" the subequence "123" based on the mapping described in A051683. |
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+0
1
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| 0, 1, 2, 3, 4, 6, 7, 8, 9, 10, 12, 13, 16, 18, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 36, 37, 40, 42, 48, 49, 50, 51, 52, 60, 61, 64, 66, 72, 73, 76, 90, 96
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Note that a(n) can be viewed as an irregular table with shape sequence 1 1 3 9 28 ... demonstrating the relationships with 1 2 5 14 42 ... cf A000108 and A000142.
0
1
2 3 4
6 7 8 9 10 12 13 16 18
24 25 26 27 28 30 31 32 ... 96
120 ...
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EXAMPLE
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The numbers 0 thru 4 map to 321,312,231,213 and 132 and are included because they avoid 123. The next number, 5, maps to 123 so is excluded from a(n).
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CROSSREFS
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Cf. A000108 A000142 A051683 A141824.
Sequence in context: A029596 A039160 A048264 this_sequence A070932 A093686 A030319
Adjacent sequences: A141822 A141823 A141824 this_sequence A141826 A141827 A141828
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KEYWORD
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more,nonn
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AUTHOR
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Alford Arnold (Alford1940(AT)aol.com), Jul 24 2008
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