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 A143657 Number of 4-noncrossing stack-free partial matching without 1-arcs. 0
 1, 1, 2, 5, 12, 32, 95, 301, 1001, 3495, 12708, 47932, 186581, 747619, 3073207 (list; graph; refs; listen; history; text; internal format)
 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. Asymptotically a(n) ~ (1.217 * 10^7)*(n^(-21/2))*(3.0382^n). LINKS Emma Y. Jin and Christian M. Reidys, RNA-LEGO: Combinatorial Design of Pseudoknot RNA, Dec 4, 2007, arXiv:0711.1405. 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. CROSSREFS Cf. A132441. Sequence in context: A218781 A002838 A076822 * A014326 A148284 A148285 Adjacent sequences:  A143654 A143655 A143656 * A143658 A143659 A143660 KEYWORD nonn AUTHOR Jonathan Vos Post, Aug 28 2008 EXTENSIONS Arxiv URL replaced by non-cached version - R. J. Mathar, Oct 30 2009 STATUS approved

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Last modified July 21 04:40 EDT 2019. Contains 325189 sequences. (Running on oeis4.)