A350373 Numbers with exactly 6 semiprime divisors.

210, 330, 390, 462, 510, 546, 570, 690, 714, 770, 798, 858, 870, 900, 910, 930, 966, 1110, 1122, 1155, 1190, 1218, 1230, 1254, 1290, 1302, 1326, 1330, 1365, 1410, 1430, 1482, 1518, 1554, 1590, 1610, 1722, 1764, 1770, 1785, 1794, 1800, 1806, 1830, 1870, 1914, 1938, 1974, 1995

Offset

1,1

Links

Table of n, a(n) for n=1..49.

Mathematica

q[n_] := DivisorSum[n, 1 &, PrimeOmega[#] == 2 &] == 6; Select[Range[2000], q] (* Amiram Eldar, Dec 28 2021 *)

Prog

(PARI) isok(k) = sumdiv(k, d, bigomega(d)==2) == 6; \\ Michel Marcus, Dec 28 2021

Crossrefs

Numbers with exactly k semiprime divisors: A346041 (k=1), A345381 (k=2), A345382 (k=3), A350371 (k=4), A350372 (k=5), this sequence (k=6), A350374 (k=7), A350375 (k=8).

Sequence in context: A127424 A074159 A033993 * A046386 A229272 A046402

Adjacent sequences: A350370 A350371 A350372 * A350374 A350375 A350376

Keyword

nonn

Author

Wesley Ivan Hurt, Dec 27 2021

Status

approved