First: y increases in steps of 2 while x increases in steps of 1.
Second: take 1 off the y values then halve them: 3, 4, 5, ...
Third: take 2 off these values: 1, 2, 3, ...
Fourth: now we see these are the x values, so reverse the process:
x+2, double it, add 1: 2(x+2)+1=2x+4+1=2x+5 so y=2x+5. That's the rule.