%I #9 Feb 17 2021 04:18:59
%S 1,1,2,1,2,1,3,1,2,1,2,2,3,1,2,1,3,1,2,1,3,2,3,1,2,1,3,1,2,1,3,2,3,1,
%T 2,1,3,2,2,1,2,2,4,1,2,1,3,1,2,1,2,2,3,1,3,1,5,1,2,1,2,2,3,1,2,1,3,1,
%U 2,1,2,3,4,1,2,1,3,1,2,2,2,2,4,1,2,1,3,1,3,1,3,2,3,1,2,1,3,1,2,1,2,2,3,1,2
%N a(n) is the number of integers k > 0 such that (n*k+1)/(k^2+1) is an integer.
%e a(57)=5 because (57*k+1)/(k^2+1) is an integer for k = 1,2,5,7,57.
%o (PARI) a(n) = sum(k=1, n, denominator((n*k+1)/(k^2+1)) == 1); \\ _Michel Marcus_, Feb 17 2021
%K nonn
%O 1,3
%A _Benoit Cloitre_, Dec 29 2001
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