Respuesta :

1 & 3 goes up by 2
3 & 6 goes up by 3
6 & 10 goes up by 4
10 & 15 goes by 5
15 & 21 goes by 6
21 & 28 goes by 7
28 & 36 goes by 8
 Mainly you are just going up by one
 
The next two terms should be 45 and 55