OFFSET
1,1
COMMENTS
The sequence is finite and contains 2520 numbers.
To build a such number, first place the digits 1 to 5, and then insert the digit 6 anywhere but not after the digit 5, then the digits 7, 8 and 9. The order of the digits from 1 to 5 is imposed.
There are 5 ways to place the digits 6, 7 ways to place the digit 7, 8 ways to place the digit 8 and 9 ways to place the digit 9.
We obtain 5*7*8*9 = 2520 numbers.
LINKS
Michel Lagneau, Table of n, a(n) for n = 1..2520
CROSSREFS
KEYWORD
nonn,base,fini,full,less
AUTHOR
Michel Lagneau, Nov 22 2014
STATUS
approved