cp's OEIS Frontend

A293915 Number of linear chord diagrams having n chords and minimal chord length two.

%I A293915 #7 Oct 25 2017 18:08:36
%S A293915 1,4,26,230,2509,32422,484180,8203519,155460169,3257843351,
%T A293915 74802301553,1867393802229,50358879172771,1458899632505052,
%U A293915 45185432509804438,1489952528266230695,52112346134820625126,1926974225717684659004,75110765705496454871866
%N A293915 Number of linear chord diagrams having n chords and minimal chord length two.
%H A293915 Alois P. Heinz, <a href="/A293915/b293915.txt">Table of n, a(n) for n = 2..404</a>
%F A293915 Recurrence: (24*n^2 - 182*n + 339)*a(n) = (96*n^3 - 800*n^2 + 1894*n - 991)*a(n-1) - (96*n^4 - 824*n^3 + 1804*n^2 + 650*n - 3571)*a(n-2) + 2*(144*n^4 - 1788*n^3 + 8032*n^2 - 15489*n + 10821)*a(n-3) - 2*(144*n^4 - 2028*n^3 + 10452*n^2 - 23337*n + 18994)*a(n-4) + (96*n^4 - 1592*n^3 + 9452*n^2 - 23794*n + 21419)*a(n-5) + (96*n^3 - 1040*n^2 + 3550*n - 3841)*a(n-6) + (24*n^2 - 134*n + 181)*a(n-7). - _Vaclav Kotesovec_, Oct 25 2017
%F A293915 a(n) ~ (exp(-1) - exp(-2)) * 2^(n + 1/2) * n^n / exp(n). - _Vaclav Kotesovec_, Oct 25 2017
%Y A293915 Column k=2 of A293881.
%K A293915 nonn
%O A293915 2,2
%A A293915 _Alois P. Heinz_, Oct 19 2017