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.
EXAMPLE
Triangle begins:
1:
2:
3: 1
4:
5: 2
6: 1
7: 1 1
8:
9: 1 1
10: 2
11: 3
12: 1
13: 1 2
For example, the weakly increasing prime indices of 105 are (2,3,4), with prime indices ((1),(2),(1,1)), so row 105 is (1,2,1,1).
MATHEMATICA
primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Join@@Table[Join@@primeMS/@primeMS[n], {n, 100}]
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Gus Wiseman, Sep 29 2022
STATUS
approved