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A350371
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Numbers with exactly 4 semiprime divisors.
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5
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60, 84, 90, 120, 126, 132, 140, 150, 156, 168, 198, 204, 220, 228, 234, 240, 260, 264, 270, 276, 280, 294, 306, 308, 312, 315, 336, 340, 342, 348, 350, 364, 372, 378, 380, 408, 414, 440, 444, 456, 460, 476, 480, 490, 492, 495, 516, 520, 522, 525, 528, 532, 550, 552, 558
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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q[n_] := DivisorSum[n, 1 &, PrimeOmega[#] == 2 &] == 4; Select[Range[600], q] (* Amiram Eldar, Dec 28 2021 *)
spd4Q[n_]:=Count[Divisors[n], _?(PrimeOmega[#]==2&)]==4; Select[Range[600], spd4Q] (* Harvey P. Dale, Apr 30 2023 *)
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PROG
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(PARI) isok(k) = sumdiv(k, d, bigomega(d)==2) == 4; \\ Michel Marcus, Dec 28 2021
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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