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%I #26 Mar 05 2021 03:30:23
%S 2,21,22,23,26,29,201,202,203,205,206,209,210,211,213,214,215,217,218,
%T 219,221,222,223,226,227,229,230,231,233,235,237,238,239,241,246,247,
%U 249,251,253,254,255,257,258,259,262,263,265,266,267,269,271,273,274
%N Squarefree numbers beginning with 2.
%C Intersection of A005117 and A217394. - _Michel Marcus_, Sep 14 2013
%C Lower density is 3/(10*Pi^2), upper density is 20/(9*Pi^2). - _Charles R Greathouse IV_, Nov 05 2017
%H Amiram Eldar, <a href="/A077678/b077678.txt">Table of n, a(n) for n = 1..10000</a>
%t s2Q[n_]:=First[IntegerDigits[n]]==2 && 1==Max@@Last/@FactorInteger[n]; Select[Range[274],s2Q[#] &] (* _Jayanta Basu_, May 22 2013 *)
%o (PARI) is(n)=n>1 && digits(n)[1]==2 && issquarefree(n) \\ _Charles R Greathouse IV_, Nov 05 2017
%Y Cf. A077677, A077679, A077680, A077681, A077682, A077683, A077684, A077685.
%K base,easy,nonn
%O 1,1
%A _Amarnath Murthy_, Nov 16 2002
%E More terms from _Sascha Kurz_, Jan 28 2003
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