A296514 Positive numbers whose decimal expansion contains a 3-digit substring abc such that c > a > b.

102, 103, 104, 105, 106, 107, 108, 109, 203, 204, 205, 206, 207, 208, 209, 213, 214, 215, 216, 217, 218, 219, 304, 305, 306, 307, 308, 309, 314, 315, 316, 317, 318, 319, 324, 325, 326, 327, 328, 329, 405, 406, 407, 408, 409, 415, 416, 417, 418, 419, 425, 426, 427, 428, 429

Offset

1,1

Comments

The number of n-digit numbers that start with this substring is 12*10^(n-2), n>=3, hence about 12% of n-digit numbers are of this kind, n>=3. None of the numbers that start with this substring begin with 9.

Links

Table of n, a(n) for n=1..55.

Example

The 3-digit numbers with this substring are 102, 103, ..., 109, ... 809, 819, ..., 879 (there are 120 of these).  The next numbers after 879 are 1020, 1021, etc. since they contain the string 102.
There are numbers of any length n, n>=3, with this substring, such as *213 or 213** where * is free since the string 213 is already there.

Crossrefs

Sequence in context: A031962 A303504 A135601 * A164856 A160712 A162198

Adjacent sequences: A296511 A296512 A296513 * A296515 A296516 A296517

Keyword

nonn,base

Author

Enrique Navarrete, Dec 26 2017

Status

approved