All combinations of four digits from 1 to 9

All combinations of four digits from 1 to 9

In our life, numbers are very useful. Please arrange the three numbers 1, 9 and 1,

119 fire call, life related

Here is a set of numbers in a pyramid arrangement
Here's a set of numbers arranged in a pyramid -- 1 -- 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 6. The eighth number in line 19 is____ -What line is 1 / 28

Odd lines are negative, even lines are positive
The last number of each line,
1=1
3=1+2
6=1+2+3
……
So the last number in line 18 is: 1 / (1 + 2 + 3 +...) +18）=1/171
So the eighth number in line 19 is: - 1 / (171 + 8) = - 1 / 179
28=1+2+3+4+5+6+7
So - 1 / 28 is on line 7, number 7

First line 1 second line 2 3 third line 4 5 6 fourth line 7 8 9 10 1090 in which rows and columns

1
2 3
4 5 6
…………
One number in the first line
Two numbers in the second line
Three numbers in the third line
…………
Number of N in the nth row
(1+n)n/2=1090
(1+n)n=2180
N = 46 (integer)
（1+46）*46/2=1081
1090-1081=9
So 1090 is number 47, number 9!