Please help, what is the domain of the graph?

Suppose the first five terms of a sequence are 4, 5, 9, 27, 123. how could the next term in the sequence be generated?

Can someone me and do the problem plz so i can understand it more better

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?