cp's OEIS Frontend

A302494 Products of distinct primes of squarefree index.

%I A302494 #7 Apr 10 2018 21:48:04
%S A302494 1,2,3,5,6,10,11,13,15,17,22,26,29,30,31,33,34,39,41,43,47,51,55,58,
%T A302494 59,62,65,66,67,73,78,79,82,83,85,86,87,93,94,101,102,109,110,113,118,
%U A302494 123,127,129,130,134,137,139,141,143,145,146,149,155,157,158,163
%N A302494 Products of distinct primes of squarefree index.
%C A302494 A prime index of n is a number m such that prime(m) divides n.
%e A302494 Entry A302242 describes a correspondence between positive integers and multiset multisystems. In this case it gives the following sequence of set systems.
%e A302494 01: {}
%e A302494 02: {{}}
%e A302494 03: {{1}}
%e A302494 05: {{2}}
%e A302494 06: {{},{1}}
%e A302494 10: {{},{2}}
%e A302494 11: {{3}}
%e A302494 13: {{1,2}}
%e A302494 15: {{1},{2}}
%e A302494 17: {{4}}
%e A302494 22: {{},{3}}
%e A302494 26: {{},{1,2}}
%e A302494 29: {{1,3}}
%e A302494 30: {{},{1},{2}}
%e A302494 31: {{5}}
%e A302494 33: {{1},{3}}
%e A302494 34: {{},{4}}
%e A302494 39: {{1},{1,2}}
%t A302494 Select[Range[100],Or[#===1,SquareFreeQ[#]&&And@@SquareFreeQ/@PrimePi/@FactorInteger[#][[All,1]]]&]
%o A302494 (PARI) is(n) = if(bigomega(n)!=omega(n), return(0), my(f=factor(n)[, 1]~); for(k=1, #f, if(!issquarefree(primepi(f[k])) && primepi(f[k])!=1, return(0)))); 1 \\ _Felix Fröhlich_, Apr 10 2018
%Y A302494 Cf. A000961, A001222, A003963, A005117, A007716, A056239, A270995, A275024, A276625, A277098, A279785, A281113, A296120, A301754, A302242, A302243.
%K A302494 nonn
%O A302494 1,2
%A A302494 _Gus Wiseman_, Apr 08 2018