A293917 Number of linear chord diagrams having n chords and minimal chord length four.

1, 19, 252, 3441, 52938, 919077, 17783732, 379205917, 8832657552, 223147872970, 6078406509776, 177602480890788, 5541376133638552, 183896037042429100, 6468180930063929404, 240368899912444102612, 9410883311417206598912, 387192534875365889313239

Offset: 4

Author

Alois P. Heinz, Oct 19 2017

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 4..404

Crossrefs

Column k=4 of A293881.

Formula

a(n) ~ (exp(-3) - exp(-4)) * 2^(n + 1/2) * n^n / exp(n). - Vaclav Kotesovec, Oct 25 2017