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A276894 Number of ordered set partitions of [n] such that for each block b the smallest integer interval containing b has at most four elements. 3
1, 1, 3, 13, 75, 466, 3272, 26032, 232820, 2304600, 25003176, 295139034, 3767545662, 51729553992, 760326663792, 11913105530016, 198246166468224, 3492246172917240, 64928731038925800, 1270685662509505560, 26112819120798942120, 562241528313838756560 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..449

FORMULA

a(n) ~ exp(3) * n!. - Vaclav Kotesovec, Sep 22 2016

MATHEMATICA

b[n_, m_, l_List] := b[n, m, l] = If[n == 0, m!, Sum[b[n - 1, Max[m, j], Append[ReplacePart[l, 1 -> Nothing], If[j <= m, 0, j]]], {j, Append[l, m + 1] ~Complement~ {0}}]]; a[n_] := b[n, 0, {0, 0, 0}]; Table[a[n], {n, 0, 21}] (* Jean-Fran├žois Alcover, Jul 18 2017, after Alois P. Heinz *)

CROSSREFS

Column k=4 of A276890.

Cf. A276720.

Sequence in context: A009382 A110193 A038762 * A074517 A251658 A330047

Adjacent sequences:  A276891 A276892 A276893 * A276895 A276896 A276897

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Sep 21 2016

STATUS

approved

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Last modified April 13 06:52 EDT 2021. Contains 342935 sequences. (Running on oeis4.)