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A124097 Numbers which are "easy" to key on a standard telephone keypad. 1
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 14, 15, 21, 22, 23, 24, 25, 26, 32, 33, 35, 36, 41, 42, 44, 45, 47, 48, 51, 52, 53, 54, 55, 56, 57, 58, 59, 62, 63, 65, 66, 68, 69, 70, 74, 75, 77, 78, 80, 84, 85, 86, 87, 88, 89, 90, 95, 96, 98, 99, 111, 112, 114, 115, 121, 122, 123, 124 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

On a standard telephone keypad, i.e. 123 | 456 | 789 | 0, a number is "easy" to key in if each adjacent pair of digits in the number are the same, or are adjacent - either horizontally or vertically or diagonally. For example, adjacent to the 2 key are 1 and 3 (horizontal), 5 (vertical) and 4 and 6 (diagonal) so any of these digits could come after a 2 (but not 7, 8, 9 or 0).

LINKS

N. J. A. Sloane, Table of n, a(n) for n = 1..10001

EXAMPLE

126 is a term since the 1 and 2 keys are adjacent and the 6 is diagonally adjacent to the 2.

CROSSREFS

Sequence in context: A330982 A033108 A049811 * A180478 A062461 A178843

Adjacent sequences:  A124094 A124095 A124096 * A124098 A124099 A124100

KEYWORD

nonn,dumb,base

AUTHOR

Paul Richards, Dec 12 2006

STATUS

approved

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Last modified April 7 19:49 EDT 2020. Contains 333306 sequences. (Running on oeis4.)