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A332944
Number of entries in the fourth blocks of all set partitions of [n] when blocks are ordered by increasing lengths.
2
1, 21, 166, 1247, 7855, 47245, 284968, 1741235, 10782872, 69537976, 471717130, 3336898255, 24584784957, 189704257763, 1530649634720, 12849873769593, 111945035887787, 1011184665775833, 9458811859041042, 91480934118104305, 913112230809837136, 9391472034599656856
OFFSET
4,2
LINKS
MAPLE
b:= proc(n, i, t) option remember; `if`(n=0, [1, 0], `if`(i>n, 0,
add((p-> p+`if`(t>0 and t-j<1, [0, p[1]*i], 0))(b(n-i*j, i+1,
max(0, t-j))/j!*combinat[multinomial](n, i$j, n-i*j)), j=0..n/i)))
end:
a:= n-> b(n, 1, 4)[2]:
seq(a(n), n=4..25);
CROSSREFS
Column k=4 of A319298.
Sequence in context: A146301 A338891 A126993 * A022681 A266733 A107970
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Mar 03 2020
STATUS
approved