A386977 Products of 3 distinct semiprimes.

216, 240, 336, 360, 504, 528, 540, 560, 600, 624, 756, 792, 810, 816, 840, 880, 900, 912, 936, 1000, 1040, 1104, 1134, 1176, 1188, 1224, 1232, 1260, 1320, 1350, 1360, 1368, 1392, 1400, 1404, 1456, 1488, 1500, 1520, 1560, 1656, 1764, 1776, 1782, 1836, 1840, 1848

Offset

1,1

Links

Alois P. Heinz, Table of n, a(n) for n = 1..10000

Example

216 = 4 * 6 * 9.

Maple

q:= n-> (l-> l=[3$2] or nops(l)>2 and add(i, i=l)=6)(ifactors(n)[2][..., 2]):
select(q, [$1..2000])[];  # Alois P. Heinz, Aug 12 2025

Mathematica

Select[Range@ 2000, MemberQ[{{3, 3}, {1, 1, 4}, {1, 2, 3}, {2, 2, 2}, {1, 1, 1, 3}, {1, 1, 2, 2}, {1, 1, 1, 1, 2}, {1, 1, 1, 1, 1, 1}}, Sort[Last /@ FactorInteger@ #]] &] (* Giovanni Resta, Aug 12 2025 *)

Crossrefs

Cf. A001222, A001358 (semiprimes), A007304 (sphenic numbers).

Subsequence of A046306.

Sequence in context: A018863 A003998 A335544 * A230400 A001239 A184088

Adjacent sequences: A386974 A386975 A386976 * A386978 A386979 A386980

Keyword

nonn

Author

Ian Hahus, Aug 11 2025

Status

approved