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A081306
Numbers n with prime factors less than 2*spf(n), where spf(m) is the smallest prime factor of m (A020639).
8
1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 16, 17, 18, 19, 23, 24, 25, 27, 29, 31, 32, 35, 36, 37, 41, 43, 45, 47, 48, 49, 53, 54, 59, 61, 64, 67, 71, 72, 73, 75, 77, 79, 81, 83, 89, 91, 96, 97, 101, 103, 107, 108, 109, 113, 121, 125, 127, 128, 131, 135, 137, 139, 143, 144
OFFSET
1,2
COMMENTS
A081303(a(n)) < 0, A006530(a(n)) < A020639(a(n))*2.
LINKS
MAPLE
filter:= proc(n) local F;
F:= numtheory:-factorset(n);
max(F) < 2*min(F);
end proc:
select(filter, [$1..200]); # Robert Israel, Mar 28 2018
MATHEMATICA
Select[Range[200], Max[F = FactorInteger[#][[All, 1]]] < 2 Min[F]&] (* Jean-François Alcover, Mar 04 2019 *)
CROSSREFS
Complement of A069900.
Union of {1} and A069899. [R. J. Mathar, Sep 18 2008]
Sequence in context: A073491 A066311 A069899 * A130073 A133812 A115661
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Mar 17 2003
STATUS
approved