OFFSET
1,1
COMMENTS
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.
The median of a multiset is either the middle part (for odd length), or the average of the two middle parts (for even length).
All terms are squarefree.
EXAMPLE
The terms together with their prime indices begin:
4: {1,1}
54: {1,2,2,2}
81: {2,2,2,2}
90: {1,2,2,3}
100: {1,1,3,3}
126: {1,2,2,4}
135: {2,2,2,3}
140: {1,1,3,4}
189: {2,2,2,4}
198: {1,2,2,5}
MATHEMATICA
prix[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Select[Range[100], PrimeOmega[#]==2*Median[prix[#]]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Apr 20 2023
STATUS
approved