%I #16 Nov 18 2020 01:34:02
%S 1,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,
%T 109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,
%U 199,211,223,227,229,233,239,241,251,257,263,269,271
%N 19-rough numbers: positive integers that have no prime factors less than 19.
%C Or, positive integers relatively prime to 510510 = 2*3*5*7*11*13*17.
%H Harvey P. Dale, <a href="/A166061/b166061.txt">Table of n, a(n) for n = 1..1000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/RoughNumber.html">Rough Number</a>
%H <a href="/index/Sk#smooth">Index entries for sequences related to smooth numbers</a> [From _Michael B. Porter_, Oct 10 2009]
%F a(n) = k*n + O(1) where k = 17017/3072 = 5.539388.... In particular, k*n - 31 < a(n) < k*n + 25. - _Charles R Greathouse IV_, Sep 24 2018
%e 437 = 19 * 23 is in the sequence since the two prime factors, 19 and 23, are not less than 19.
%t Join[{1},Select[Range[300],Min[Transpose[FactorInteger[#]][[1]]]>18&]] (* _Harvey P. Dale_, Feb 18 2015 *)
%o (PARI) isA166061(n) = gcd(n,510510)==1 \\ _Michael B. Porter_, Oct 10 2009
%Y k-rough numbers: A000027, A005408, A007310, A007775, A008364, A008365, A008366, A166061, A166063.
%K easy,nonn
%O 1,2
%A _Michael B. Porter_, Oct 05 2009