This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A077683 #15 Mar 05 2021 03:30:37 %S A077683 7,70,71,73,74,77,78,79,701,703,705,706,707,709,710,713,714,715,717, %T A077683 718,719,721,723,727,730,731,733,734,737,739,741,742,743,745,746,749, %U A077683 751,753,754,755,757,758,759,761,762,763,766,767,769,770,771,773,777,778 %N A077683 Squarefree numbers beginning with 7. %C A077683 Lower density is 3/(35*Pi^2), upper density is 5/(6*Pi^2). - _Charles R Greathouse IV_, Nov 05 2017 %H A077683 Amiram Eldar, <a href="/A077683/b077683.txt">Table of n, a(n) for n = 1..10000</a> %o A077683 (PARI) is(n)=n>6 && digits(n)[1]==7 && issquarefree(n) \\ _Charles R Greathouse IV_, Nov 05 2017 %Y A077683 Intersection of A005117 and A217400. %Y A077683 Cf. A077677, A077678, A077679, A077680, A077681, A077682, A077684, A077685. %K A077683 base,easy,nonn %O A077683 1,1 %A A077683 _Amarnath Murthy_, Nov 16 2002 %E A077683 More terms from _Sascha Kurz_, Jan 28 2003