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A322511
Nonnegative numbers whose digits can be formed by typing adjacent keys on a 123-456-789 keypad without repeating a digit and without changing direction.
0
1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 14, 21, 23, 25, 32, 36, 41, 45, 47, 52, 54, 56, 58, 63, 65, 69, 74, 78, 85, 87, 89, 96, 98, 123, 147, 258, 321, 369, 456, 654, 741, 789, 852, 963, 987
OFFSET
1,2
COMMENTS
Subsequence of A280593.
Diagonal moves are not allowed.
EXAMPLE
The keypad is:
+---+---+---+
| 1 | 2 | 3 |
+---+---+---+
| 4 | 5 | 6 |
+---+---+---+
| 7 | 8 | 9 |
+---+---+---+
258 can be formed in a straight line, while 256 cannot, even though 256 is formed with adjacent digits. Therefore 258 is a part of this sequence while 256 is not.
CROSSREFS
KEYWORD
nonn,full,fini,base
AUTHOR
Jason Jewell, Dec 13 2018
STATUS
approved