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Nonnegative numbers whose digits can be formed by typing adjacent keys on a 123-456-789-0XX keypad without repeating a digit.
3

%I #30 Jul 08 2018 02:36:33

%S 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,

%T 69,70,74,78,85,87,89,96,98,123,125,145,147,214,236,254,256,258,321,

%U 325,365,369,412,452,456,458,470,478,521,523,541,547,563,569,587,589,632,652,654,658,698,741

%N Nonnegative numbers whose digits can be formed by typing adjacent keys on a 123-456-789-0XX keypad without repeating a digit.

%C A subsequence of A010784. - _FUNG Cheok Yin_, Jul 05 2018

%H FUNG Cheok Yin, <a href="/A281942/b281942.txt">Table of n, a(n) for n = 1..725</a>

%e The keypad is:

%e +---+---+---+

%e | 1 | 2 | 3 |

%e +---+---+---+

%e | 4 | 5 | 6 |

%e +---+---+---+

%e | 7 | 8 | 9 |

%e +---+---+---+

%e | 0 | x | x |

%e +---+---+---+

%e It is visibly obvious that 470 can be formed on the keypad.

%Y Cf. A010784, A280593, A280594, A280595, A281943, A215009.

%K nonn,fini,base,full

%O 1,3

%A _FUNG Cheok Yin_, Feb 02 2017

%E Initial 0 added by _N. J. A. Sloane_, Feb 05 2017