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A304713 Squarefree numbers whose prime indices are pairwise indivisible. Heinz numbers of strict integer partitions with pairwise indivisible parts. 18
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: A102553 A069161 * A319327 A319319 A003277 A117287

Adjacent sequences:  A304710 A304711 A304712 * A304714 A304715 A304716

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 17 2018

STATUS

approved

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Last modified November 17 21:02 EST 2018. Contains 317278 sequences. (Running on oeis4.)