Answer:
a_n = a_(n-1) + 3 where a_1 = 2
a_7 = 20
Step-by-step explanation:
here a_n is denoting the number of hexagons that show up in the diagram.
starting with a_1 = 2
a_2 = a_1 + 3 = 2 + 3 = 5
a_3 = a_2 + 3 = 5 + 3 = 8
a_4 = a_3 + 3 = 8 + 3 = 11
a_5 = a_4 + 3 = 11 + 3 = 14
a_6 = a_5 + 3 = 14 + 3 = 17
a_7 = a_6 + 3 = 17 + 3 = 20
