A350424 Numbers for which the number of their semiprime divisors sets a new record.

4, 12, 30, 60, 180, 210, 420, 1260, 2310, 4620, 13860, 30030, 60060, 180180, 510510, 1021020, 3063060, 9699690, 19399380, 58198140, 223092870, 446185740, 1338557220, 6469693230, 12939386460, 38818159380, 194090796900, 200560490130, 401120980260, 1203362940780, 6016814703900

Offset: 1

Author

Hugo Pfoertner, Dec 30 2021

Keywords

• nonn

Comments

Aside from the first term a(1)=4, the sequence appears to be a subset of A129912. - Bill McEachen, Dec 31 2021

Crossrefs

A350425 gives the corresponding number of semiprime divisors.

Cf. A129912, A220264.

Programs

Mathematica

nspd[n_]:=Count[Divisors[n],?(PrimeOmega[#]==2&)]; DeleteDuplicates[Table[{n,nspd[n]},{n,194*10^5}],GreaterEqual[#1[[2]],#2[[2]]]&][[;;,1]] (* The program generates the first 19 terms of the sequence. *) (* _Harvey P. Dale, Dec 03 2024 *)