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A324849 Positive integers divisible by none of their prime indices > 1.

%I A324849 #12 Mar 21 2019 04:16:06
%S A324849 1,2,3,4,5,7,8,9,10,11,13,14,16,17,19,20,21,22,23,25,26,27,29,31,32,
%T A324849 33,34,35,37,38,39,40,41,43,44,46,47,49,50,51,52,53,57,58,59,61,62,63,
%U A324849 64,65,67,68,69,70,71,73,74,76,77,79,80,81,82,83,85,86,87
%N A324849 Positive integers divisible by none of their prime indices > 1.
%C A324849 A prime index of n is a number m such that prime(m) divides n.
%H A324849 Robert Israel, <a href="/A324849/b324849.txt">Table of n, a(n) for n = 1..10000</a>
%e A324849 The sequence of terms together with their prime indices begins:
%e A324849    1: {}
%e A324849    2: {1}
%e A324849    3: {2}
%e A324849    4: {1,1}
%e A324849    5: {3}
%e A324849    7: {4}
%e A324849    8: {1,1,1}
%e A324849    9: {2,2}
%e A324849   10: {1,3}
%e A324849   11: {5}
%e A324849   13: {6}
%e A324849   14: {1,4}
%e A324849   16: {1,1,1,1}
%e A324849   17: {7}
%e A324849   19: {8}
%e A324849   20: {1,1,3}
%e A324849   21: {2,4}
%e A324849   22: {1,5}
%e A324849   23: {9}
%e A324849   25: {3,3}
%p A324849 filter:= proc(n) andmap(t -> not ((n/numtheory:-pi(t))::integer), numtheory:-factorset(n) minus {2}) end proc:
%p A324849 select(filter, [$1..200]); # _Robert Israel_, Mar 20 2019
%t A324849 Select[Range[100],!Or@@Cases[If[#==1,{},FactorInteger[#]],{p_,_}:>If[p==2,False,Divisible[#,PrimePi[p]]]]&]
%o A324849 (PARI) is(n) = my(f=factor(n)[, 1]~, idc=[]); for(k=1, #f, idc=concat(idc, [primepi(f[k])])); for(t=1, #idc, if(idc[t]==1, next); if(n%idc[t]==0, return(0))); 1 \\ _Felix Fröhlich_, Mar 21 2019
%Y A324849 Complement of A324771.
%Y A324849 Cf. A003963, A056239, A112798, A120383, A289509, A304360, A306844.
%Y A324849 Cf. A324695, A324741, A324743, A324756, A324758, A324765, A324846, A324847, A324848, A324850, A324852, A324853, A324856.
%K A324849 nonn
%O A324849 1,2
%A A324849 _Gus Wiseman_, Mar 18 2019