What number should appear next in this sequence? 2 ; 8 ; 11 ; 18 ; 30 ; 47 ; 78 ; ?

Answer 1

124.
Let's state the previous number x
The 2nd previous number y
and the positioned number z.
Starting with 2 and 8 (x+y+1)=z
And from 8 and 11 (x+y)-1=z
It keeps going and going.