

A215009


Numbers which are "easy" to key on a computer numpad.


4



0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 20, 21, 23, 25, 32, 36, 41, 45, 47, 52, 54, 56, 58, 63, 65, 69, 74, 78, 85, 87, 89, 96, 98, 101, 120, 121, 123, 125, 141, 145, 147, 202, 210, 212, 214, 232, 236, 252, 254, 256, 258, 320, 321, 323, 325, 363, 365, 369, 410
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OFFSET

1,3


COMMENTS

On a computer numpad, a number is "easy" to key in if each adjacent pair of digits in the number are adjacent  either horizontally or vertically.
Here are two ways to type these numbers. Example for 25:
1. Press the numpad "2" key. Then let go and press "5".
2. Press the "2" and slide your finger on the numeric keypad up to the "5".
Method 2 shows that the sequence contains only numbers in which every pair of adjacent digits are distinct.
Pressing a numeric key followed by "0" and pressing a numeric key is equivalent to selecting "101" or "202".


LINKS

Arkadiusz Wesolowski, Table of n, a(n) for n = 1..10000
Wikipedia, Numeric keypad
Index entries for 10automatic sequences.


EXAMPLE

25 is a term because the 2 and 5 keys are adjacent.


MATHEMATICA

lst = {}; Do[If[StringCount[ToString[n], {"00", "03", "04", "05", "06", "07", "08", "09", "11", "13", "15", "16", "17", "18", "19", "22", "24", "26", "27", "28", "29", "30", "31", "33", "34", "35", "37", "38", "39", "40", "42", "43", "44", "46", "48", "49", "50", "51", "53", "55", "57", "59", "60", "61", "62", "64", "66", "67", "68", "70", "71", "72", "73", "75", "76", "77", "79", "80", "81", "82", "83", "84", "86", "88", "90", "91", "92", "93", "94", "95", "97", "99", "102", "201"}] == 0, AppendTo[lst, n]], {n, 0, 410}]; lst


CROSSREFS

Cf. A082390. Subsequence of A043096.
Sequence in context: A322605 A175740 A320321 * A281943 A120003 A333223
Adjacent sequences: A215006 A215007 A215008 * A215010 A215011 A215012


KEYWORD

base,dumb,easy,nonn


AUTHOR

Arkadiusz Wesolowski, Jul 31 2012


STATUS

approved



