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%I #5 Jul 01 2019 02:02:25
%S 1,1,1,3,6,20,71,431,11111,1096517,3060614764,139873870750394,
%T 2228164248308209927663,137936736998106949095632586591612,
%U 1537967284879934603600637815040145351018766857006
%N a(n) is the smallest integer such that 1/a(1)^2 + 1/a(2)^2 + ... + 1/a(n-1)^2 + 1/a(n)^2 is less than Pi.
%F a(n) = ceiling(sqrt(Pi - Sum_{i=1..n-1} 1/a(i)^2)).
%e a(4)=3 because Pi - 1/a(1)^2 - 1/a(2)^2 - 1/a(3)^2 = Pi - 1 - 1 - 1 = 0.1415926... and 3 is the smallest integer such that 1/3^2 = 0.1111111... < 0.1415926...
%o (PARI) l(x)=ceil(sqrt(1/x)) k=Pi;for(T=1,50,print(l(k));k=k-1/l(k)^2)
%K nonn
%O 1,4
%A Hauke Worpel (hw1(AT)email.com), Nov 11 2006
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