OFFSET
1,2
COMMENTS
A prime index of n is a number m such that prime(m) divides n. Two or more numbers are coprime if no pair of them has a common divisor other than 1. A single number is not considered coprime unless it is equal to 1.
The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).
EXAMPLE
Sequence of terms together with their sets of prime indices begins:
01 : {}
02 : {1}
03 : {2}
05 : {3}
06 : {1,2}
07 : {4}
10 : {1,3}
11 : {5}
13 : {6}
14 : {1,4}
15 : {2,3}
17 : {7}
19 : {8}
22 : {1,5}
23 : {9}
26 : {1,6}
29 : {10}
30 : {1,2,3}
MATHEMATICA
Select[Range[100], Or[#===1, SquareFreeQ[#]&&(PrimeQ[#]||CoprimeQ@@PrimePi/@FactorInteger[#][[All, 1]])]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Apr 13 2018
STATUS
approved