Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #12 Mar 17 2024 05:42:57
%S 1,6,217,13997,1283817,151778430,21902350480,3726598826676,
%T 729894290301789,161683308639785288,39960246577221138239,
%U 10900687898284398341055,3253179971490906621196740,1054372896576358319473872858,368810384314446516250937494104
%N a(n) = A258220(2n,n).
%H Vaclav Kotesovec, <a href="/A292692/b292692.txt">Table of n, a(n) for n = 0..290</a> (terms 0..200 from Alois P. Heinz)
%F a(n) ~ c * d^n * n! / sqrt(n), where d = 25.81959672662517201... and c = 0.28310309251343879... - _Vaclav Kotesovec_, Dec 01 2017
%F Conjecture: d = (51*sqrt(17) - 107)/4. - _Vaclav Kotesovec_, Mar 17 2024
%Y Cf. A258220.
%K nonn
%O 0,2
%A _Alois P. Heinz_, Sep 20 2017