OFFSET
1,2
COMMENTS
Start with an integer partition y of n. Given a multiset, take the multiset of its multiplicities. Repeat until a multiset of size 1 is obtained. If this multiset is {2}, we say that y reduces to 2. For example, we have (3211) -> (211) -> (21) -> (11) -> (2), so (3211) reduces to 2.
EXAMPLE
The a(7) = 12 partitions:
(43), (52), (61),
(322), (331), (511),
(2221), (3211), (4111),
(22111), (31111),
(211111).
MATHEMATICA
Table[Length[Select[IntegerPartitions[n], NestWhile[Sort[Length/@Split[#]]&, #, Length[#]>1&]=={2}&]], {n, 30}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 12 2018
STATUS
approved