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%I #13 Sep 26 2021 19:42:45
%S 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,21,23,25,27,29,31,35,
%T 37,41,43,47,49,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,
%U 131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,202
%N Numbers with no two-digit factors (apart from itself).
%H David A. Corneth, <a href="/A052425/b052425.txt">Table of n, a(n) for n = 1..10000</a>
%e From _David A. Corneth_, Aug 20 2020: (Start)
%e 202 is in the sequence as the divisors of 202 are 1, 2, 101, 202 and none have two digits (in base 10).
%e 20 isn't in the sequence as 20 is divisible by 10 which has two digits in base 10 and isn't 20. (End)
%t ntdfQ[n_]:=Union[IntegerLength[#]==2&/@Most[Divisors[n]]]=={False}; Join[ {1},Select[Range[250],ntdfQ]] (* _Harvey P. Dale_, Sep 26 2021 *)
%o (PARI) is(n) = for(i = 10, min(n-1, 99), if(n % i == 0, return(0))); 1 \\ _David A. Corneth_, Aug 20 2020
%K base,nonn
%O 1,2
%A _Henry Bottomley_, Mar 14 2000
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