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: .
4: 1
5: .
6: 2
7: .
8: 1 1
9: 1
10: 3
11: .
12: 2 2
13: .
14: 4
15: 2
16: 1 1 1
17: .
18: 2 1
19: .
20: 3 3
For example, the prime indices of 900 are (1,1,2,2,3,3), so row 900 is 3 - (1,1,2,2,3) + 1 = (3,3,2,2,1).
MATHEMATICA
primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Table[If[n==1, {}, 1+Last[primeMS[n]]-Most[primeMS[n]]], {n, 100}]
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Gus Wiseman, Dec 20 2022
STATUS
approved