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Numbers with no two-digit factors (including itself).
7

%I #14 Mar 11 2018 22:18:58

%S 1,2,3,4,5,6,7,8,9,101,103,107,109,113,127,131,137,139,149,151,157,

%T 163,167,173,179,181,191,193,197,199,202,206,211,214,218,223,226,227,

%U 229,233,239,241,251,254,257,262,263,269,271,274,277,278,281,283,293,298,302,303,307,309,311,313,314

%N Numbers with no two-digit factors (including itself).

%C Numbers of the form k*m where 1 <= k <= 9 and either m=1 or A020639(m) >= 100. - _Robert Israel_, Mar 11 2018

%H Robert Israel, <a href="/A052426/b052426.txt">Table of n, a(n) for n = 1..10000</a>

%p lpf:= n -> min(numtheory:-factorset(n)):

%p filter:= proc(n) local k;

%p for k from 9 to 1 by -1 do

%p if n mod k = 0 then return(lpf(n/k) > 100) fi

%p od

%p end proc:

%p select(filter, [$1..1000]); # _Robert Israel_, Mar 11 2018

%Y Cf. A020639.

%K base,nonn

%O 1,2

%A _Henry Bottomley_, Mar 14 2000

%E Missing terms 277, 281, 283, 293, 307, 311, 313 inserted by _Robert Israel_, Mar 11 2018