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 A056971 Number of (binary) heaps on n elements. 56
 1, 1, 1, 2, 3, 8, 20, 80, 210, 896, 3360, 19200, 79200, 506880, 2745600, 21964800, 108108000, 820019200, 5227622400, 48881664000, 319258368000, 3143467008000, 25540669440000, 299677188096000, 2261626278912000, 25732281217843200, 241240136417280000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS A sequence {a_i}_{i=1..N} forms a (binary) heap if it satisfies a_i (f-> a(f)*       binomial(n-1, f)*a(n-1-f))(min(g-1, n-g/2)))(2^ilog2(n)))     end: seq(a(n), n=0..28);  # Alois P. Heinz, Feb 14 2019 MATHEMATICA a = 1; a = 1; For[n = 2, n <= 50, n++, h = Floor[Log[2, n + 1]] - 1; b = 2^h - 1; r = n - 1 - 2*b; r1 = r - Floor[r/2^h]*(r - 2^h); r2 = r - r1; a[n] = Binomial[n - 1, b + r1]*a[b + r1]*a[b + r2]]; Table[a[n], {n, 0, 26}] (* Jean-François Alcover, Oct 22 2012, translated from Maple program *) CROSSREFS Cf. A053644, A056972, A132862. Column k=2 of A273693. Column k=0 of A306343 and of A306393. Sequence in context: A073268 A073190 A066051 * A108125 A175490 A118854 Adjacent sequences:  A056968 A056969 A056970 * A056972 A056973 A056974 KEYWORD nonn AUTHOR EXTENSIONS More terms from Sascha Kurz, Mar 24 2002 Offset and some terms corrected by Alois P. Heinz, Nov 21 2007 STATUS approved

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Last modified October 14 05:08 EDT 2019. Contains 327995 sequences. (Running on oeis4.)