login
A297152
Positive numbers whose decimal expansion contains a 3-digit substring abc such that b > a > c.
0
120, 130, 140, 150, 160, 170, 180, 190, 230, 231, 240, 241, 250, 251, 260, 261, 270, 271, 280, 281, 290, 291, 340, 341, 342, 350, 351, 352, 360, 361, 362, 370, 371, 372, 380, 381, 382, 390, 391, 392, 450, 451, 452, 453, 460, 461, 462, 463, 470, 471, 472, 473
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.
EXAMPLE
The 3-digit numbers with this substring are 120, 130, ..., 190, ... 890, 891, ..., 897 (there are 120 of these). The next numbers after 879 are 1200, 1201, etc. since they contain the string 120.
There are numbers of any length n, n>=3, that contain this substring, such as *231 or 231** where * is free since the substring 231 is already there.
CROSSREFS
Sequence in context: A030501 A271578 A376151 * A074302 A095631 A248662
KEYWORD
nonn,base
AUTHOR
Enrique Navarrete, Dec 26 2017
STATUS
approved