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%I #10 Jul 28 2024 03:50:48
%S 4,4,9,4,4,9,4,4,25,9,4,4,4,4,9,4,49,25,4,9,4,4,9,4,4,25,4,4,9,4,4,9,
%T 4,4,49,9,4,4,4,9,4,121,4,25,9,4,4,9,4,4,49,4,25,4,9,4,4,9,4,4,169,9,
%U 4,25,4,4,4,9,4,9,4,9,4,4,4,4,4,4,9,4,4
%N The single square referenced in A190641.
%H Robert Price, <a href="/A283670/b283670.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A283671(n)^2 = A249739(A190641(n))^2. - _Amiram Eldar_, Jul 28 2024
%e A190641(4) = 12, 12 = 2*2*3, so 12 has only one square factor, namely 4.
%t f[n_] := Module[{f = FactorInteger[n], ind}, ind = Position[f[[;;, 2]], _?(# > 1 &)]; If[Length[ind] == 1, f[[ind[[1, 1]],1]]^2, Nothing]]; Array[f, 300] (* _Amiram Eldar_, Jul 28 2024 *)
%o (PARI) lista(kmax) = for(k = 1, kmax, my(f = factor(k)); if(#select(x -> (x>1), f[,2]) == 1, for(i = 1, #f~, if(f[i,2] > 1, print1(f[i,1]^2, ", "); break)))); \\ _Amiram Eldar_, Jul 28 2024
%Y Cf. A190641, A249739, A283671.
%K nonn,changed
%O 1,1
%A _Robert Price_, Mar 13 2017
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