A077683 - OEIS

%I #15 Mar 05 2021 03:30:37

%S 7,70,71,73,74,77,78,79,701,703,705,706,707,709,710,713,714,715,717,

%T 718,719,721,723,727,730,731,733,734,737,739,741,742,743,745,746,749,

%U 751,753,754,755,757,758,759,761,762,763,766,767,769,770,771,773,777,778

%N Squarefree numbers beginning with 7.

%C Lower density is 3/(35*Pi^2), upper density is 5/(6*Pi^2). - _Charles R Greathouse IV_, Nov 05 2017

%H Amiram Eldar, <a href="/A077683/b077683.txt">Table of n, a(n) for n = 1..10000</a>

%o (PARI) is(n)=n>6 && digits(n)[1]==7 && issquarefree(n) \\ _Charles R Greathouse IV_, Nov 05 2017

%Y Intersection of A005117 and A217400.

%Y Cf. A077677, A077678, A077679, A077680, A077681, A077682, A077684, A077685.

%K base,easy,nonn

%O 1,1

%A _Amarnath Murthy_, Nov 16 2002

%E More terms from _Sascha Kurz_, Jan 28 2003