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.
LINKS
EXAMPLE
The sequence of terms together with their prime indices begins:
1: {}
35: {3,4}
143: {5,6}
209: {5,8}
247: {6,8}
391: {7,9}
493: {7,10}
629: {7,12}
667: {9,10}
851: {9,12}
901: {7,16}
1073: {10,12}
1219: {9,16}
1333: {11,14}
1457: {11,15}
1537: {10,16}
1891: {11,18}
1961: {12,16}
2021: {14,15}
2201: {11,20}
MATHEMATICA
primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Select[Range[1000], !PrimeQ[#]&&SquareFreeQ[#]&&SameQ@@Total/@primeMS/@primeMS[#]&];
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 30 2019
STATUS
approved