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.
EXAMPLE
The terms together with their prime indices begin:
4: {1,1}
9: {2,2}
12: {1,1,2}
16: {1,1,1,1}
25: {3,3}
30: {1,2,3}
40: {1,1,1,3}
48: {1,1,1,1,2}
49: {4,4}
63: {2,2,4}
64: {1,1,1,1,1,1}
70: {1,3,4}
81: {2,2,2,2}
84: {1,1,2,4}
MATHEMATICA
prix[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Select[Range[100], MemberQ[Accumulate[prix[#]], Total[prix[#]]/2]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jun 06 2023
STATUS
approved