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 A129873 Sequence s_n arising in enumeration of arrays of directed blocks (see Quaintance reference for precise definition). 3
 2, 3, 8, 13, 38, 64, 196, 337, 1062, 1851, 5948, 10468, 34120, 60488, 199316, 355369, 1181126, 2115577, 7080928, 12731141, 42860534, 77306428, 261542752, 473018396, 1607076200, 2913321828, 9934255472, 18045744424, 61732449648, 112340143632 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES Jocelyn Quaintance, Combinatoric Enumeration of Two-Dimensional Proper Arrays, Discrete Math., 307 (2007), 1844-1864. LINKS Table of n, a(n) for n=1..30. FORMULA See Quaintance reference for generating functions that produce A129872-A129886. G.f.: S(t) satisfies (8*t^4 - t^2)*S(t)^3 + (24*t^3 - 2*t^2 - 4*t)*S(t)^2 + (24*t^2 + 2^t - 3)*S(t) + 8*t + 3 = 0. - Michel Marcus, Mar 29 2013 PROG (PARI) listsn(m) = {my(S = t*O(t)); for (n= 1, m+1, S = (- 8*t - 3 - (8*t^4 - t^2)*S^3 - (24*t^3 - 2*t^2 - 4*t)*S^2)/(24*t^2 + 2*t - 3); ); return(vector(m, i , polcoeff(S, i, t))); } \\ Michel Marcus, Mar 29 2013 CROSSREFS Sequence in context: A366020 A294151 A294566 * A025575 A077055 A327868 Adjacent sequences: A129870 A129871 A129872 * A129874 A129875 A129876 KEYWORD nonn AUTHOR N. J. A. Sloane, May 26 2007 EXTENSIONS More terms from Michel Marcus, Mar 29 2013 STATUS approved

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Last modified October 4 19:37 EDT 2023. Contains 365888 sequences. (Running on oeis4.)