login
a(1) = 4, and for any n > 1, a(n+1) is the a(n)-th squarefree number.
1

%I #8 Aug 07 2022 07:52:45

%S 4,5,6,7,10,14,21,33,53,85,138,222,366,599,985,1613,2651,4357,7169,

%T 11795,19401,31913,52487,86347,142021,233615,384277,632091,1039741,

%U 1710305,2813358,4627790,7612435,12521926,20597674,33881799,55733298,91677666,150803687

%N a(1) = 4, and for any n > 1, a(n+1) is the a(n)-th squarefree number.

%C See A071255 for a similar sequence.

%C The ratio a(n+1)/a(n) tends to Pi^2/6 (A013661) as n tends to infinity.

%H Rémy Sigrist, <a href="/A356398/a356398.txt">C program</a>

%F a(n+1) = A005117(a(n)).

%e a(1) = 4 and the fourth squarefree number is 5, so a(2) = 5.

%o (C) See Links section.

%Y Cf. A005117, A006508, A007097, A013661, A071255.

%K nonn

%O 1,1

%A _Rémy Sigrist_, Aug 05 2022