OFFSET
0,4
COMMENTS
These could be described as transitive integer partitions.
A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
EXAMPLE
The a(1) = 1 through a(8) = 8 integer partitions:
(1) (11) (21) (211) (41) (321) (421) (3221)
(111) (1111) (221) (411) (2221) (4211)
(2111) (2211) (3211) (22211)
(11111) (21111) (4111) (32111)
(111111) (22111) (41111)
(211111) (221111)
(1111111) (2111111)
(11111111)
MATHEMATICA
Table[Length[Select[IntegerPartitions[n], SubsetQ[#, PrimePi/@First/@Join@@FactorInteger/@DeleteCases[#, 1]]&]], {n, 0, 30}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Mar 16 2019
STATUS
approved