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%I #12 Aug 02 2019 23:22:46
%S 1,1,2,2,4,2,6,4,6,5,12,5,16,9,11,12,24,9,28,13,19,16,36,13,33,22,34,
%T 25,56,16,64,36,46,38,56,29,86,44,56,37,94,28,98,46,55,52,106,37,95,
%U 49,80,64,134,49,107,67,106,82,170,46,182,94,111,104,149,63,212,104,146,78
%N a(1)=1; a(n) = Sum_{1<=k<=n, gcd(k,n)=1} a(floor(sqrt(k))).
%e The positive integers that are <12 and are coprime to 12 are 1,5,7,11. The floors of the square roots of these are 1,2,2,3. So a(12) = a(1) + a(2) + a(2) + a(3) = 1 + 1 + 1 + 2 = 5.
%t a = {1}; Do[s = 0; For[j = 1, j < n, j++, If[GCD[j, n] == 1, s = s + a[[Floor[Sqrt[j]]]]]]; AppendTo[a, s], {n, 2, 80}]; a (* _Stefan Steinerberger_, Dec 19 2007 *)
%K nonn
%O 1,3
%A _Leroy Quet_, Nov 26 2007
%E More terms from _Stefan Steinerberger_, Dec 19 2007