Find the arithmetic sequence whose 1st term is 1 and the 1st, 2nd and 6th terms form a geometric sequence

Answer 1

1 / (d + 1) = (d + 1) / (5d + 1)

5d + 1 = (d + 1)^2 ... d^2 - 3d = 0 ... d = 3

An = 3n - 2