254988

Appears in sequences

• The number of interior points that are intersections of exactly two chords for a 2n-gon where all its vertices are joined by lines (cf. A006561).at n=26A352144
• a(0) = a(1) = 1; a(n) = 3 * Sum_{k=0..n-2} a(k) * a(n-k-2).at n=12A354734