

A302478


Products of prime numbers of squarefree index.


24



1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 20, 22, 24, 25, 26, 27, 29, 30, 31, 32, 33, 34, 36, 39, 40, 41, 43, 44, 45, 47, 48, 50, 51, 52, 54, 55, 58, 59, 60, 62, 64, 65, 66, 67, 68, 72, 73, 75, 78, 79, 80, 81, 82, 83, 85, 86, 87, 88, 90, 93, 94
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OFFSET

1,2


COMMENTS

A prime index of n is a number m such that prime(m) divides n.


LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..1000


EXAMPLE

Entry A302242 describes a correspondence between positive integers and multiset multisystems. In this case it gives the following sequence of set multisystems.
01: {}
02: {{}}
03: {{1}}
04: {{},{}}
05: {{2}}
06: {{},{1}}
08: {{},{},{}}
09: {{1},{1}}
10: {{},{2}}
11: {{3}}
12: {{},{},{1}}
13: {{1,2}}
15: {{1},{2}}
16: {{},{},{},{}}
17: {{4}}
18: {{},{1},{1}}
20: {{},{},{2}}
22: {{},{3}}
24: {{},{},{},{1}}
25: {{2},{2}}
26: {{},{1,2}}
27: {{1},{1},{1}}
29: {{1,3}}
30: {{},{1},{2}}
31: {{5}}
32: {{},{},{},{},{}}


MATHEMATICA

Select[Range[100], Or[#===1, And@@SquareFreeQ/@PrimePi/@FactorInteger[#][[All, 1]]]&]


PROG

(PARI) ok(n)={!#select(p>!issquarefree(primepi(p)), factor(n)[, 1])} \\ Andrew Howroyd, Aug 26 2018


CROSSREFS

Cf. A000961, A001222, A003963, A005117, A007716, A050320, A056239, A063834, A076610, A270995, A275024, A281113, A296119, A301753, A302242, A302243, A302491.
Sequence in context: A023801 A332107 A267305 * A356939 A113619 A325114
Adjacent sequences: A302475 A302476 A302477 * A302479 A302480 A302481


KEYWORD

nonn


AUTHOR

Gus Wiseman, Apr 08 2018


STATUS

approved



