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 A005983 Number of 4 up, 4 down, 4 up, ... permutations of length 4n+1. (Formerly M5347) 3
 1, 1, 70, 26599, 33757360, 107709888805, 726401013530416, 9197888739246870571, 200656681438694771057920, 7065183006232334215872360169, 381446884048286939903298793116160, 30299510478473850351087119774475282895, 3422529682416045761005260546463028151218176 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). P. R. Stein, personal communication. LINKS Alois P. Heinz, Table of n, a(n) for n = 0..132 P. R. Stein and N. J. A. Sloane, Correspondence, 1975 MAPLE b:= proc(u, o, t) option remember; `if`(u+o=0, 1, add(`if`(t=4,       b(o-j, u+j-1, 1), b(u+j-1, o-j, t+1)), j=1..o))     end: a:= n-> b(0, 4*n+1, 0): seq(a(n), n=0..20);  # Alois P. Heinz, Oct 06 2013 MATHEMATICA b[u_, o_, t_] := b[u, o, t] = If[u+o == 0, 1, Sum[If[t == 4, b[o-j, u+j-1, 1], b[u+j-1, o-j, t+1]], {j, 1, o}]] ; a[n_] := b[0, 4*n+1, 0]; Table[a[n], {n, 1, 20}] (* Jean-François Alcover, Nov 25 2014, after Alois P. Heinz *) CROSSREFS Cf. A229885. Sequence in context: A145410 A177638 A274646 * A200313 A177642 A177644 Adjacent sequences:  A005980 A005981 A005982 * A005984 A005985 A005986 KEYWORD nonn AUTHOR EXTENSIONS Typo in name fixed by Alois P. Heinz, Oct 06 2013 STATUS approved

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Last modified January 22 16:47 EST 2019. Contains 319364 sequences. (Running on oeis4.)