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%I #10 Aug 27 2018 01:52:57
%S 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,
%T 32,33,34,36,39,40,41,43,44,45,47,48,50,51,52,54,55,58,59,60,62,64,65,
%U 66,67,68,72,73,75,78,79,80,81,82,83,85,86,87,88,90,93,94
%N Products of prime numbers of squarefree index.
%C A prime index of n is a number m such that prime(m) divides n.
%H Andrew Howroyd, <a href="/A302478/b302478.txt">Table of n, a(n) for n = 1..1000</a>
%e Entry A302242 describes a correspondence between positive integers and multiset multisystems. In this case it gives the following sequence of set multisystems.
%e 01: {}
%e 02: {{}}
%e 03: {{1}}
%e 04: {{},{}}
%e 05: {{2}}
%e 06: {{},{1}}
%e 08: {{},{},{}}
%e 09: {{1},{1}}
%e 10: {{},{2}}
%e 11: {{3}}
%e 12: {{},{},{1}}
%e 13: {{1,2}}
%e 15: {{1},{2}}
%e 16: {{},{},{},{}}
%e 17: {{4}}
%e 18: {{},{1},{1}}
%e 20: {{},{},{2}}
%e 22: {{},{3}}
%e 24: {{},{},{},{1}}
%e 25: {{2},{2}}
%e 26: {{},{1,2}}
%e 27: {{1},{1},{1}}
%e 29: {{1,3}}
%e 30: {{},{1},{2}}
%e 31: {{5}}
%e 32: {{},{},{},{},{}}
%t Select[Range[100],Or[#===1,And@@SquareFreeQ/@PrimePi/@FactorInteger[#][[All,1]]]&]
%o (PARI) ok(n)={!#select(p->!issquarefree(primepi(p)), factor(n)[,1])} \\ _Andrew Howroyd_, Aug 26 2018
%Y Cf. A000961, A001222, A003963, A005117, A007716, A050320, A056239, A063834, A076610, A270995, A275024, A281113, A296119, A301753, A302242, A302243, A302491.
%K nonn
%O 1,2
%A _Gus Wiseman_, Apr 08 2018
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