The general process is as follows
On the other hand, from big to small.
0 1 2 does not start.
There are 32 10 1 species at the beginning of 3.
There are four kinds at the beginning of 4: 432 1 4320 43 10 (the first three kinds are 43)+42 10 (n3).
5 starts with 54 # # 6 species (54-32,31,30,21,20, 10) plus 53,52. And the ones starting with 53 and 52 are equal to all the cases starting with 4, so N5=6+N4= 10.
And so on, as long as the numbers 65, 76, 87, 98 at the beginning of several cases.
N3= 1
N4=4
N5= 10
n6 = 10+N5 =( 1+2+3+4)+N5 = 20
n7 = 15+N6 =( 1+2+3+4+5)+N5 = 35
N8 = 2 1+N7 =( 1+2+3+4+5+6)+N5 = 56
n9 = 28+N8 =( 1+2+3+4+5+6+7)+N5 = 84
N (1+2+3+4+5+6+7+8+9) = 210 species.
Attachment: 76 # # Starting numbering method
76 54 43 32 265 438+0 65 438+00 * * 65 438+0+2+3+4+5 species.
53 42 3 1 20
52 4 1 30
5 1 40
50
Finally finished. . .