Source of the n=71 certificate
Retrieved on 23 August 2026 from Achim Flammenkamp's
no-three-in-line database.
Its dated notes say that Marijn Heule found the first solution on
17 August 2026 in symmetry class rct4.
The exact entry came from the database lookup endpoint
/cgi-bin/cgiwrap/achim/script_lookup?para=FIXED, with POST fields
symm=c, size=71, and index=1. The response identified it as the first
rct4 solution and reported database cut date 19 August 2026. The untouched
one-line code is n71-rct4.code.
The database documentation specifies one symmetry character followed by two
encoded column positions for each row. Its current 90-character alphabet is
recorded in decode_database.py; that decoder rejects wrong lengths,
out-of-grid columns, and duplicate row positions before emitting the plain
coordinate certificate.