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 A356398 #8 Aug 07 2022 07:52:45 %S A356398 4,5,6,7,10,14,21,33,53,85,138,222,366,599,985,1613,2651,4357,7169, %T A356398 11795,19401,31913,52487,86347,142021,233615,384277,632091,1039741, %U A356398 1710305,2813358,4627790,7612435,12521926,20597674,33881799,55733298,91677666,150803687 %N A356398 a(1) = 4, and for any n > 1, a(n+1) is the a(n)-th squarefree number. %C A356398 See A071255 for a similar sequence. %C A356398 The ratio a(n+1)/a(n) tends to Pi^2/6 (A013661) as n tends to infinity. %H A356398 Rémy Sigrist, <a href="/A356398/a356398.txt">C program</a> %F A356398 a(n+1) = A005117(a(n)). %e A356398 a(1) = 4 and the fourth squarefree number is 5, so a(2) = 5. %o A356398 (C) See Links section. %Y A356398 Cf. A005117, A006508, A007097, A013661, A071255. %K A356398 nonn %O A356398 1,1 %A A356398 _Rémy Sigrist_, Aug 05 2022