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:
6: {1,2}
12: {1,1,2}
18: {1,2,2}
21: {2,4}
24: {1,1,1,2}
36: {1,1,2,2}
48: {1,1,1,1,2}
54: {1,2,2,2}
63: {2,2,4}
65: {3,6}
72: {1,1,1,2,2}
96: {1,1,1,1,1,2}
MATHEMATICA
Select[Range[2, 100], PrimePi[FactorInteger[#][[-1, 1]]]==2*PrimePi[FactorInteger[#][[1, 1]]]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Apr 05 2023
STATUS
approved