OFFSET
1,2
COMMENTS
In an antichain of sets, no edge is a proper subset of any other.
EXAMPLE
The prime indices of 65 are {3,6} with binary indices {{1,2},{2,3}} so 65 is in the sequence.
The prime indices of 255 are {2,3,7} with binary indices {{2},{1,2},{1,2,3}} so 255 is not in the sequence.
MATHEMATICA
stableQ[u_, Q_]:=!Apply[Or, Outer[#1=!=#2&&Q[#1, #2]&, u, u, 1], {0, 1}];
bix[n_]:=Join@@Position[Reverse[IntegerDigits[n, 2]], 1];
prix[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Select[Range[100], stableQ[bix/@prix[#], SubsetQ]&]
CROSSREFS
Contains all powers of primes A000961.
These antichains are counted by A325109.
A048143 counts connected antichains of sets.
A070939 gives length of binary expansion.
A089259 counts set multipartitions of integer partitions.
A116540 counts normal set multipartitions.
A371451 counts carry-connected components of binary indices.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Apr 01 2024
STATUS
approved