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A301762
Number of ways to choose a constant rooted partition of each part in a rooted partition of n.
1
1, 1, 2, 4, 7, 12, 21, 34, 55, 90, 143, 220, 347, 528, 805, 1226, 1831, 2719, 4048, 5940, 8710, 12714, 18403, 26529, 38220, 54679, 77899, 110810, 156848, 221181, 311635, 436705, 610597, 852125, 1184928, 1644136, 2276551, 3142523, 4328960, 5953523, 8167209
OFFSET
1,3
COMMENTS
A rooted partition of n is an integer partition of n - 1.
FORMULA
O.g.f.: Product_{n>0} 1/(1 - d(n-1) x^n) where d(n) = A000005(n) and d(0) = 1.
EXAMPLE
The a(5) = 7 rooted twice-partitions where the latter rooted partitions are constant: (3), (111), (2)(), (11)(), (1)(1), (1)()(), ()()()().
MATHEMATICA
Table[Sum[Product[If[k===1, 1, DivisorSigma[0, k-1]], {k, ptn}], {ptn, IntegerPartitions[n-1]}], {n, 20}]
KEYWORD
nonn
AUTHOR
Gus Wiseman, Mar 26 2018
STATUS
approved