There are about 400 non-lettered routes. Even if an average route met fifty others (surely an overestimate?), if they were randomly distributed you would expect only one route in eight to meet the route numbered one higher than itself. So statistically you would expect 400/8 = 50 such pairs, about six (400/8x8)runs of three, odds of better than 3 to 1 on there being a sequence of four, and only a 10% chance of there being a sequence of five.
160/161/162 all run along Chislehurst High Street
196/197/198 - the 196 terminates on the west side of Norwood Junction station, the 197 calls on the east side. The 197 and 198 meet in Croydon
230/231/232 all meet at Turnpike Lane station
There is no U6 or U8, but you can do the other U routes in sequence, and even go round again as the U10 meets the U1
H9-19 is broken into a sequence of five and another of three, because the H13 does not meet the H14 and the H15 and H16 no longer operate.