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A304713 Squarefree numbers whose prime indices are pairwise indivisible. Heinz numbers of strict integer partitions with pairwise indivisible parts. 9
1, 2, 3, 5, 7, 11, 13, 15, 17, 19, 23, 29, 31, 33, 35, 37, 41, 43, 47, 51, 53, 55, 59, 61, 67, 69, 71, 73, 77, 79, 83, 85, 89, 91, 93, 95, 97, 101, 103, 107, 109, 113, 119, 123, 127, 131, 137, 139, 141, 143, 145, 149, 151, 155, 157, 161, 163, 165, 167, 173 (list; graph; refs; listen; history; text; internal format)
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).

LINKS

Table of n, a(n) for n=1..60.

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

Cf. A000009, A005117, A006126, A056239, A073576, A285572, A285573, A293606, A293993, A302696, A302796, A303362, A303365, A304711.

Sequence in context: A072697 A102553 A069161 * A003277 A117287 A121615

Adjacent sequences:  A304710 A304711 A304712 * A304714 A304715 A304716

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 17 2018

STATUS

approved

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Last modified July 22 00:25 EDT 2018. Contains 312888 sequences. (Running on oeis4.)