OFFSET
1,2
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.
Also Heinz numbers of partitions either constant or relatively prime (A338553). The Heinz number of a partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k), giving a bijective correspondence between positive integers and integer partitions.
MATHEMATICA
Select[Range[100], #==1||PrimePowerQ[#]||GCD@@PrimePi/@First/@FactorInteger[#]==1&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Nov 03 2020
STATUS
approved