If we are to carefully study the given numbers in the sequence, we can say that they are in arithmetic sequence wherein the difference between the first two terms is 5. Also, the difference between the next two terms is also five. The nth term for the arithmetic sequence may be calculated through the equation,
An = A₁ + (n - 1)d
Substituting the known values,
An = 1 + (n - 1)(5)