A215009 -id:A215009 - cp's OEIS frontend

A281942 Nonnegative numbers whose digits can be formed by typing adjacent keys on a 123-456-789-0XX keypad without repeating a digit.

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, 69, 70, 74, 78, 85, 87, 89, 96, 98, 123, 125, 145, 147, 214, 236, 254, 256, 258, 321, 325, 365, 369, 412, 452, 456, 458, 470, 478, 521, 523, 541, 547, 563, 569, 587, 589, 632, 652, 654, 658, 698, 741

Offset: 1

FUNG Cheok Yin, Feb 02 2017

A subsequence of A010784. - FUNG Cheok Yin, Jul 05 2018

			The keypad is:
+---+---+---+
| 1 | 2 | 3 |
+---+---+---+
| 4 | 5 | 6 |
+---+---+---+
| 7 | 8 | 9 |
+---+---+---+
| 0 | x | x |
+---+---+---+
It is visibly obvious that 470 can be formed on the keypad.

FUNG Cheok Yin, Table of n, a(n) for n = 1..725

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

Initial 0 added by N. J. A. Sloane, Feb 05 2017

A281943 Nonnegative numbers whose digits can be formed by typing adjacent keys on a 789-456-123-00X keypad without repeating a digit.

Original entry on oeis.org

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, 102, 120, 123, 125, 145, 147, 201, 210, 214, 236, 254, 256, 258, 320, 321, 325, 365, 369, 410, 412, 452, 456, 458, 478, 520, 521, 523, 541, 547, 563, 569, 587

Offset: 1

FUNG Cheok Yin, Feb 02 2017

A subsequence of A010784. - FUNG Cheok Yin, Jul 05 2018

			The keypad is:
+---+---+---+
| 7 | 8 | 9 |
+---+---+---+
| 4 | 5 | 6 |
+---+---+---+
| 1 | 2 | 3 |
+---+---+---+
|   0   | x |
+---+---+---+
It is visibly obvious that 5210 can be formed on the keypad.

FUNG Cheok Yin, Table of n, a(n) for n = 1..1082

Cf. A010784, A280593, A280594, A280595, A281942, A215009.

Initial 0 added by N. J. A. Sloane, Feb 05 2017

A283161 Natural numbers whose digits can be formed by typing non-adjacent keys on a 123-456-789 keypad without repeating a digit.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 13, 15, 16, 17, 18, 19, 24, 26, 27, 28, 29, 31, 34, 35, 37, 38, 39, 42, 43, 46, 48, 49, 51, 53, 57, 59, 61, 62, 64, 67, 68, 71, 72, 73, 75, 76, 79, 81, 82, 83, 84, 86, 91, 92, 93, 94, 95, 97, 135, 137, 138, 139, 153, 157, 159, 167, 168, 173, 175, 176, 179, 183, 186, 193, 195

Offset: 1

FUNG Cheok Yin, Mar 02 2017

Or say numbers which are "very difficult" to be typed on a keypad without the zero. (See description of A215009.)

			The keypad is:
+-----+
|1|2|3|
+-+-+-+
|4|5|6|
+-+-+-+
|7|8|9|
+-+-+-+
It is visibly obvious that 168 can be formed on the keypad, and each pairwise digits of 168 are not adjacent.

FUNG Cheok Yin, Table of n, a(n) for n = 1..453
FUNG Cheok Yin, C++ program

Cf. A280593, A215009, A006506(3)

no = IntegerDigits @ {12,14,23,25,34,36,45,47,56,58,69,78,89}; Sort[ FromDigits /@ Flatten[ Permutations /@ Select[ Subsets[ Range@ 9, {1, 9}], Intersection[ Subsets[#, {2}], no] == {} &], 1]] (* Giovanni Resta, Apr 06 2017 *)

cp's OEIS Frontend

A281942 Nonnegative numbers whose digits can be formed by typing adjacent keys on a 123-456-789-0XX keypad without repeating a digit.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Extensions

A281943 Nonnegative numbers whose digits can be formed by typing adjacent keys on a 789-456-123-00X keypad without repeating a digit.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Extensions

A283161 Natural numbers whose digits can be formed by typing non-adjacent keys on a 123-456-789 keypad without repeating a digit.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Mathematica