A086975 Numbers of the form p^2 * q * r with primes p < q < r.

60, 84, 132, 140, 156, 204, 220, 228, 260, 276, 308, 315, 340, 348, 364, 372, 380, 444, 460, 476, 492, 495, 516, 532, 564, 572, 580, 585, 620, 636, 644, 693, 708, 732, 740, 748, 765, 804, 812, 819, 820, 836, 852, 855, 860, 868, 876, 884, 940, 948, 988

Offset: 1

Author

Reinhard Zumkeller, Jul 25 2003

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A086974 and of A085987.

Cf. A000005, A001221, A001222, A020639.

Programs

Mathematica

Select[Range[1000], FactorInteger[#][[;;, 2]] == {2, 1, 1} &] (* Amiram Eldar, Sep 15 2024 *)

PARI

is(k) = factor(k)[, 2] == [2, 1, 1]~; \\ Amiram Eldar, Sep 15 2024

Formula

A001221(a(n)) = 3.

A001222(a(n)) = 4.

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

A000005(a(n)) = 12. - Amiram Eldar, Sep 15 2024