OFFSET
1,3
LINKS
EXAMPLE
The a(8)=8 twice-partitions of type (Q,R,Q) are:
((8)), ((71)), ((62)), ((53)),
((521)), ((4)(31)), ((31)(4)), ((431)).
MATHEMATICA
nn=20;
sps[{}]:={{}}; sps[set:{i_, ___}]:=Join@@Function[s, Prepend[#, s]&/@sps[Complement[set, s]]]/@Cases[Subsets[set], {i, ___}];
Table[Total[Total[Factorial/@Length/@Select[sps[Sort[#]], SameQ@@Total/@#&]]&/@Select[IntegerPartitions[n], UnsameQ@@#&]], {n, nn}]
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Gus Wiseman, Dec 18 2016
STATUS
approved