OFFSET
1,3
LINKS
Pontus von Brömssen, Illustration of all optimal polyominoes for 1 <= n <= 23.
Pontus von Brömssen, Illustration of the unique polyomino with 6 cells and a(6)=13 lines.
Pontus von Brömssen, Illustration of the unique polyomino with 13 cells and a(13)=60 lines.
FORMULA
a(n+1)-n <= a(n) <= n*(n-1)/2, with equality in the second part if and only if n <= 4 = A380991(2). The first part is equivalent to n*(n-1)/2 - a(n) being nondecreasing.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Pontus von Brömssen, Mar 09 2026
STATUS
approved