Hello, EQ Noob checking in.

[Videri]

From http://wiki.project1999.com/Experience

Lowest Level * 1.5 (Round down) or Highest Level * 0.667 (Round up) and always at least 5 levels.
Generic Examples
Level 1 can group with up to a 6
Level 20 can group up to a 30 (20 * 1.5 = 30)
Level 30 can group down to a 20 (30 * 0.667 = 20)

Rounding Examples
Level 33 can group up to a 49 (33 * 1.5 = 49.5)
Level 50 can group down to a 34 (50 * 0.67 = 33.34)

So until level 15, it’s +/-5 levels. 1 can group with 6, 5 can group with 10, 8 can group with 14. Once the highest group member is 15, you have to use the 1.5x rule.