OFFSET
1,2
COMMENTS
Maynard shows there are infinitely many integers n such that the interval [n,n+90] contains 2 primes and a number with at most 4 prime factors [Jonathan Vos Post, May 23 2012]
Subset of the 5-free numbers (numbers where each exponent in the prime factorization is <=4). - R. J. Mathar, Aug 08 2012
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
James Maynard, Bounded length intervals containing two primes and an almost-prime, arXiv:1205.5020v1 [math.NT], May 22 2012
FORMULA
EXAMPLE
88 = 2*2*2*11 is in the sequence since it has 4 prime factors
72 = 2*2*2*3*3 is not in the sequence since it has 5 prime factors
MATHEMATICA
Select[Range[100], PrimeOmega[#]<= 4 &] (* G. C. Greubel, May 24 2016 *)
PROG
(PARI) isA166718(n) = (bigomega(n) <= 4)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Michael B. Porter, Oct 20 2009
STATUS
approved