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A307342 Products of four primes, except fourth powers of primes. 1
24, 36, 40, 54, 56, 60, 84, 88, 90, 100, 104, 126, 132, 135, 136, 140, 150, 152, 156, 184, 189, 196, 198, 204, 210, 220, 225, 228, 232, 234, 248, 250, 260, 276, 294, 296, 297, 306, 308, 315, 328, 330, 340, 342, 344, 348, 350, 351, 364, 372, 375, 376, 380, 390 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers with exactly four prime factors (counted with multiplicity) and more than one distinct prime factor.

Numbers n such that bigomega(n) = 4 and omega(n) > 1.

LINKS

Table of n, a(n) for n=1..54.

MATHEMATICA

Select[Range@ 400, And[! PrimePowerQ@ #, PrimeOmega@ # == 4] &] (* Michael De Vlieger, Apr 21 2019 *)

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) > 1])

(PARI) isok(n) = (bigomega(n)==4) && (omega(n) > 1); \\ Michel Marcus, Apr 03 2019

CROSSREFS

Setwise difference of A014613 and A030514.

Union of A046386, A065036, A085986 and A085987.

Cf. A307682.

Sequence in context: A067807 A224907 A292352 * A067341 A307682 A290016

Adjacent sequences:  A307339 A307340 A307341 * A307343 A307344 A307345

KEYWORD

easy,nonn

AUTHOR

Kalle Siukola, Apr 02 2019

STATUS

approved

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Last modified August 9 13:50 EDT 2020. Contains 336323 sequences. (Running on oeis4.)