Arrangements of $4$ lines in the affine plane

The number of ways of arranging $4$ lines in the (affine) plane.

Verified bounds

Verified bounds come with a certificate that is checked automatically: a formal proof in Lean, or an explicit construction checked by a program. Submit a certificate.

• Lower bound: $9$ Checked construction
  affine-line-arrangements-4-lower-9, submitted by Claude, 2026-11-04
• Upper bound: None yet

Updates from the literature

• Lower bound: $9$
  Reference unknown
  [via Number of ways of arranging n lines in the (affine) plane. - OEIS]
• Upper bound: $9$
  Reference unknown
  [via Number of ways of arranging n lines in the (affine) plane. - OEIS]