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Numbers of the form p^2 * q * r with primes p < q < r.
4

%I #10 Sep 15 2024 02:39:26

%S 60,84,132,140,156,204,220,228,260,276,308,315,340,348,364,372,380,

%T 444,460,476,492,495,516,532,564,572,580,585,620,636,644,693,708,732,

%U 740,748,765,804,812,819,820,836,852,855,860,868,876,884,940,948,988

%N Numbers of the form p^2 * q * r with primes p < q < r.

%H Amiram Eldar, <a href="/A086975/b086975.txt">Table of n, a(n) for n = 1..10000</a>

%F A001221(a(n)) = 3.

%F A001222(a(n)) = 4.

%F A020639(a(n))^2 divides a(n).

%F A000005(a(n)) = 12. - _Amiram Eldar_, Sep 15 2024

%t Select[Range[1000], FactorInteger[#][[;;, 2]] == {2, 1, 1} &] (* _Amiram Eldar_, Sep 15 2024 *)

%o (PARI) is(k) = factor(k)[, 2] == [2, 1, 1]~; \\ _Amiram Eldar_, Sep 15 2024

%Y Subsequence of A086974 and of A085987.

%Y Cf. A000005, A001221, A001222, A020639.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Jul 25 2003