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Primitive (squarefree) elements of A199745.
1

%I #15 Dec 31 2015 16:23:15

%S 2145,2730,4641,4845,5005,5610,7410,8778,9177,11305,11730,13485,13585,

%T 17017,20010,20930,21489,21505,23529,26445,29946,31465,31857,32538,

%U 33649,34410,35409,35581,36685,38570,38874,41106,42441,43401,45066,46189,46345,47730,49569

%N Primitive (squarefree) elements of A199745.

%H Robert Israel, <a href="/A200145/b200145.txt">Table of n, a(n) for n = 1..10000</a>

%p Filter:= proc(n) local F;

%p F:= ifactors(n)[2];

%p if max(seq(f[2],f=F)) > 1 or nops(F) < 4 then return false fi;

%p F:= map(t -> t[1],F);

%p convert(F,`+`) = 2*(max(F)+min(F));

%p end proc:

%p select(Filter,[$1..10^5]); # _Robert Israel_, Dec 31 2015

%t Select[Range[50000],Max@@Last/@(fi=FactorInteger[#])==1&&Plus@@(pl=First/@fi)/2==pl[[1]]+pl[[-1]]&] (*Ray Chandler, Nov 14 2011*)

%Y Intersection of A199745 and A005117.

%K nonn

%O 1,1

%A _Ray Chandler_, Nov 14 2011