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 A177479 Number of permutations of 1..n avoiding adjacent step pattern up, down, down. 5
 1, 1, 2, 6, 21, 90, 450, 2619, 17334, 129114, 1067661, 9713682, 96393726, 1036348587, 11998603710, 148842430470, 1969461102357, 27688474234602, 412166988789642, 6476330295597051, 107117619952992966, 1860296912926495938, 33845967939906741213, 643778989807702357314 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Suppose j b(n, 0, 0): seq(a(n), n=0..30);  # Alois P. Heinz, Oct 07 2013 MATHEMATICA FullSimplify[Rest[CoefficientList[Series[(E^(3*x/2) + 2*Cos[Sqrt[3]*x/2]) / (3*Cos[Sqrt[3]*x/2] - Sqrt[3]*Sin[Sqrt[3]*x/2]), {x, 0, 20}], x] * Range[0, 20]!]] (* Vaclav Kotesovec, Aug 23 2014 *) CROSSREFS Column k=0 of A242819. Columns k=4,6 of A242784. Sequence in context: A263852 A189243 A033540 * A147719 A231166 A115089 Adjacent sequences:  A177476 A177477 A177478 * A177480 A177481 A177482 KEYWORD nonn AUTHOR Submitted independently by Signy Olafsdottir (signy06(AT)ru.is), May 09 2010 (9 terms) and R. H. Hardin, May 10 2010 (17 terms) EXTENSIONS a(18)-a(23) from Alois P. Heinz, Oct 06 2013 STATUS approved

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