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

4,2

Links

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

Formula

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

Crossrefs

Column k=4 of A293881.

Sequence in context: A018912 A021202 A125454 * A009762 A017952 A055433

Adjacent sequences: A293914 A293915 A293916 * A293918 A293919 A293920

Keyword

nonn

Author

Alois P. Heinz, Oct 19 2017

Status

approved