Explanation:

two series are formed inside this series
1st, 3rd, 5th, 7th....1
8,12,18,…
their difference is 4,6,...
2nd, 4th, 6th....2
24,36,54
Difference 12,18,...
next term is found from 1 series
next difference would be 8
so, 
18+8=26