%I #13 Apr 30 2023 11:56:44
%S 60,84,90,120,126,132,140,150,156,168,198,204,220,228,234,240,260,264,
%T 270,276,280,294,306,308,312,315,336,340,342,348,350,364,372,378,380,
%U 408,414,440,444,456,460,476,480,490,492,495,516,520,522,525,528,532,550,552,558
%N Numbers with exactly 4 semiprime divisors.
%t q[n_] := DivisorSum[n, 1 &, PrimeOmega[#] == 2 &] == 4; Select[Range[600], q] (* _Amiram Eldar_, Dec 28 2021 *)
%t spd4Q[n_]:=Count[Divisors[n],_?(PrimeOmega[#]==2&)]==4; Select[Range[600],spd4Q] (* _Harvey P. Dale_, Apr 30 2023 *)
%o (PARI) isok(k) = sumdiv(k, d, bigomega(d)==2) == 4; \\ _Michel Marcus_, Dec 28 2021
%Y Numbers with exactly k semiprime divisors: A346041 (k=1), A345381 (k=2), A345382 (k=3), this sequence (k=4), A350372 (k=5), A350373 (k=6), A350374 (k=7), A350375 (k=8).
%K nonn
%O 1,1
%A _Wesley Ivan Hurt_, Dec 27 2021
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