OFFSET
1,2
COMMENTS
A prime index of n is a number m such that prime(m) divides n. The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).
EXAMPLE
Sequence of entries together with their corresponding multiset multisystems (see A302242) begins:
1: {}
2: {{}}
3: {{1}}
5: {{2}}
7: {{1,1}}
11: {{3}}
13: {{1,2}}
15: {{1},{2}}
17: {{4}}
19: {{1,1,1}}
23: {{2,2}}
29: {{1,3}}
31: {{5}}
33: {{1},{3}}
35: {{2},{1,1}}
MATHEMATICA
Select[Range[300], SquareFreeQ[#]&&Select[Tuples[PrimePi/@First/@FactorInteger[#], 2], UnsameQ@@#&&Divisible@@#&]==={}&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, May 17 2018
STATUS
approved