Search: id:A131519
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%I A131519
%S A131519 1,6,66,714,7710,83226,898350,9696810,104667486,1129781946,12194877966,
               131631637962,
%T A131519 1420833250878,15336488688474,165542216262126,1786864380862314,19287432460962078,
%U A131519 208188743880291834,2247191437542514638,24256207433904571146,261821751919823278590
%N A131519 Number of partitions of the graph G_n (defined below) into "strokes".
%C A131519 Here G_n = {V_n, E_n}, V_n = {v_1, v_2,..., v_n}, E_n = {e_1, e_2, ..., 
               e_{n-1}, f_1, f_2, ..., f_{n-1}}. For all i, e_i = f_i = v_iv_{i+1}
%C A131519 Given an undirected graph G=(V,E), its partition into strokes is a collection 
               of directed edge-disjoint paths (viewed as sets of directed edges) 
               on V such that (i) union of any two paths is not a path; (ii) union 
               of corresponding undirected paths is E.
%F A131519 For n>4, a(n) = 11*a(n-1) - 24*a(n-3). - Max Alekseyev (maxale(AT)gmail.com), 
               Sep 29 2007
%F A131519 G.f.: x*(2*x-1)*(6*x^2+3*x-1)/(1-11*x+24*x^3). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Nov 14 2007
%e A131519 Figure for G_5 : o=o=o=o=o
%Y A131519 Cf. A131518, A131520.
%Y A131519 Sequence in context: A119210 A119234 A119232 this_sequence A022024 A129554 
               A165229
%Y A131519 Adjacent sequences: A131516 A131517 A131518 this_sequence A131520 A131521 
               A131522
%K A131519 nonn
%O A131519 1,2
%A A131519 Yasutoshi Kohmoto zbi74583(AT)boat.zero.ad.jp, Aug 15 2007, Oct 03 2007
%E A131519 More terms from Max Alekseyev (maxale(AT)gmail.com), Sep 29 2007

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