A307341 Products of four primes, not all distinct.

16, 24, 36, 40, 54, 56, 60, 81, 84, 88, 90, 100, 104, 126, 132, 135, 136, 140, 150, 152, 156, 184, 189, 196, 198, 204, 220, 225, 228, 232, 234, 248, 250, 260, 276, 294, 296, 297, 306, 308, 315, 328, 340, 342, 344, 348, 350, 351, 364, 372, 375, 376, 380, 414

Offset

1,1

Comments

Numbers with exactly four prime factors (counted with multiplicity) but fewer than four distinct prime factors.

Numbers n such that bigomega(n) = 4 and omega(n) < 4.

Links

Kalle Siukola, Table of n, a(n) for n = 1..10000

Prog

(Python 3)
import sympy
def bigomega(n): return sympy.primeomega(n)
def omega(n): return len(sympy.primefactors(n))
print([n for n in range(1, 1000) if bigomega(n) == 4 and omega(n) < 4])
(PARI) isok(n) = (bigomega(n) == 4) && (omega(n) < 4); \\ Michel Marcus, Apr 03 2019

Crossrefs

Setwise difference of A014613 and A046386.

Union of A030514, A065036, A085986 and A085987.

Sequence in context: A110893 A014613 A323350 * A046370 A103248 A286195

Adjacent sequences: A307338 A307339 A307340 * A307342 A307343 A307344

Keyword

easy,nonn

Author

Kalle Siukola, Apr 02 2019

Status

approved