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 A128768 Number of peak-avoiding compositions with positive parts. 1
 1, 1, 2, 4, 7, 13, 22, 38, 64, 107, 177, 293, 481, 789, 1291, 2110, 3445, 5621, 9167, 14947, 24366, 39716, 64732, 105500, 171941, 280220, 456687, 744280, 1212984, 1976850, 3221762, 5250655, 8557248, 13946172, 22728787, 37042274, 60369723, 98387696, 160347599 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..1000 S. Heubach and T. Mansour, Enumeration of 3-letter patterns in combinations, arXiv:math/0603285 [math.CO], 2006. FORMULA The Heubach/Mansour paper has a complicated g.f. MAPLE b:= proc(n, t, l) option remember; `if`(n=0, 1, add(       b(n-j, is(j>l), j), j=max(1, `if`(t, l, 1))..n))     end: a:= n-> b(n, false, n): seq(a(n), n=0..40);  # Alois P. Heinz, Oct 24 2017 MATHEMATICA b[n_, t_, l_] := b[n, t, l] = If[n == 0, 1, Sum[b[n - j, j > l, j], {j, Max[1, If[t, l, 1]], n}]]; a[n_] := b[n, False, n]; Table[a[n], {n, 0, 40}] (* Jean-François Alcover, Nov 11 2017, after Alois P. Heinz *) CROSSREFS Sequence in context: A101268 A188920 A281362 * A235607 A254007 A001036 Adjacent sequences:  A128765 A128766 A128767 * A128769 A128770 A128771 KEYWORD nonn AUTHOR Ralf Stephan, May 08 2007 EXTENSIONS More terms from Vladeta Jovovic, Oct 04 2007 STATUS approved

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Last modified March 22 21:49 EDT 2018. Contains 301083 sequences. (Running on oeis4.)