

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
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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



