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 A124097 Numbers which are "easy" to key on a standard telephone keypad. 1

%I

%S 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,

%T 44,45,47,48,51,52,53,54,55,56,57,58,59,62,63,65,66,68,69,70,74,75,77,

%U 78,80,84,85,86,87,88,89,90,95,96,98,99,111,112,114,115,121,122,123,124

%N Numbers which are "easy" to key on a standard telephone keypad.

%C 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).

%H N. J. A. Sloane, <a href="/A124097/b124097.txt">Table of n, a(n) for n = 1..10001</a>

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

%K nonn,dumb,base

%O 1,3

%A _Paul Richards_, Dec 12 2006

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Last modified May 31 09:30 EDT 2020. Contains 334748 sequences. (Running on oeis4.)