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A120699
Lengths of set partitions.
2
0, 1, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6
OFFSET
0,3
COMMENTS
Each n occurs Bell(n) times.
FORMULA
Sum_{n>=1} (-1)^(n+1)/a(n) = Pi/(6*sqrt(3)) + log(3)/2. - Amiram Eldar, Feb 18 2024
MATHEMATICA
Flatten[Array[PadRight[{}, BellB[#], #]&, 7, 0]] (* Paolo Xausa, Feb 13 2024 *)
CROSSREFS
Sequence in context: A251547 A084320 A161358 * A072643 A130260 A276621
KEYWORD
nonn
AUTHOR
STATUS
approved