Question 907789
-1,1,5,11,19,29,41,55


-1     2       2       0       0       0       0
1      4       2       0       0       0       0
5      6       2       0       0       0
11     8       2       0       0
19     10      2       0
29     12      2
41     14
55
The first column is our list of numbers from the series
The second column is the list of differences between each item in the series 
they increase by two each time
2,4,6,8,10,12,14 
-1,1,5,11,19,29,41,55 differ by (-1 to 1 )2 then 4 (1 to 5) then 6 (6 to 11) then 8 (11 to 19( 
The third column is the list of differences between the first differences
which is always 2
2,4,6,8,10,12,14  differ by 2