---
tag: G9M7VGCBB6
kind: conjecture
name: Second neighborhood problem
sources:
  - wikipedia: en:59632528@r1345329964
    locator: Second neighborhood problem
    note: adopted
    mention: wikipedia://en/59632528
    sections: [Statement]
same_as:
  wikidata: Q60792926
  wikipedia: Second neighborhood problem
inventory: [C7YBT20J0G]
---

## Statement

In mathematics, the **second neighborhood problem** is an unsolved problem about oriented graphs posed by Paul Seymour. Intuitively, it suggests that in a social network described by such a graph, someone will have at least as many friends-of-friends as friends.