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 Anagram Index A.  1 0 _ Anagram

 If T is the table of all !n permutations of order n arranged in lexical order (i.e., /:T is i.!n), then k is said to be the anagram index of the permutation k{T . A. applied to a cycle or direct permutation yields its anagram index: A. 0 3 2 1 is 5, as are A. 3 2 1 and A.<3 1 and A.0;2;3 1 . The expression k A. b permutes items of b by the permutation of order #b whose anagram index is k .

For example:
```   (A. 0 3 2 1) , (A. <3 1)
5 5

A. |. i.45
119622220865480194561963161495657715064383733759999999999

<: ! 45x
119622220865480194561963161495657715064383733759999999999

tap=: i.@! A. i.           NB. Table of all permutations

(tap 3);(/: tap 3);({/\ tap 3);(/:{/\ tap 3)
+-----+-----------+-----+-----------+
|0 1 2|0 1 2 3 4 5|0 1 2|0 1 5 2 4 3|
|0 2 1|           |0 2 1|           |
|1 0 2|           |1 2 0|           |
|1 2 0|           |2 0 1|           |
|2 0 1|           |1 2 0|           |
|2 1 0|           |1 0 2|           |
+-----+-----------+-----+-----------+
```
In particular, 1 A. b transposes the last two items of b, and _1 A. b reverses the list of items, and 3 A. b and 4 A. b rotate the last three items of b. For example:
```   b=: 'ABCD'

(0 3 2 1{b);(0 3 2 1 C.b);((<3 1)C.b);(3 4 A.b)
+----+----+----+----+