A350372 Numbers with exactly 5 semiprime divisors.

180, 252, 300, 360, 396, 450, 468, 504, 540, 588, 600, 612, 684, 700, 720, 756, 792, 828, 882, 936, 980, 1008, 1044, 1080, 1100, 1116, 1176, 1188, 1200, 1224, 1300, 1332, 1350, 1368, 1400, 1404, 1440, 1452, 1476, 1500, 1512, 1548, 1575, 1584, 1620, 1656, 1692, 1700

Offset

1,1

Links

Table of n, a(n) for n=1..48.

Mathematica

q[n_] := DivisorSum[n, 1 &, PrimeOmega[#] == 2 &] == 5; Select[Range[1700], q] (* Amiram Eldar, Dec 28 2021 *)

Prog

(PARI) isok(k) = sumdiv(k, d, bigomega(d)==2) == 5; \\ Michel Marcus, Dec 28 2021

Crossrefs

Numbers with exactly k semiprime divisors: A346041 (k=1), A345381 (k=2), A345382 (k=3), A350371 (k=4), this sequence (k=5), A350373 (k=6), A350374 (k=7), A350375 (k=8).

Sequence in context: A309380 A030636 A378430 * A179643 A379098 A160134

Adjacent sequences: A350369 A350370 A350371 * A350373 A350374 A350375

Keyword

nonn

Author

Wesley Ivan Hurt, Dec 27 2021

Status

approved