OFFSET
1,3
COMMENTS
This sequence is the second row of Jin and Reidys table, p. 15; the first row, number of 3-noncrossing stack-free partial matching without 1-arcs, is A132441.
LINKS
Emma Y. Jin and Christian M. Reidys, RNA-LEGO: Combinatorial Design of Pseudoknot RNA, arXiv:0711.1405 [q-bio.BM], 2007.
FORMULA
a(n) = C_4(n,h) = SUM[b=0..{h-1}](-1)^{h-b-1}{h-1 Choose b}{T}_4(h-2h+2b+2,b+1); where the T function is defined in Jin and Reidys.
Asymptotically a(n) ~ (1.217 * 10^7)*(n^(-21/2))*(3.0382^n).
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jonathan Vos Post, Aug 28 2008
STATUS
approved