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%I #5 May 21 2021 11:18:18
%S 1,1,2,3,4,4,6,6,7,8,10,8,12,10,9,12,16,14,18,16,15,18,22,16,21,20,21,
%T 20,28,20,30,24,21,28,25,28,36,30,31,32,40,34,42,36,33,38,46,32,43,42,
%U 33,40,52,42,47,40,45,50,58,40,60,46,45,48,49,44,66,56,49,48,70,56,72
%N a(n) = n - phi(n - phi(n)), where phi is the Euler totient function.
%C If p is prime, a(p) = p - phi(p - phi(p)) = p - phi(1) = p - 1. - _Wesley Ivan Hurt_, May 21 2021
%F a(n) = n - A000010(A051953(n)).
%t Table[n - EulerPhi[n - EulerPhi[n]], {n, 100}]
%Y Cf. A000010 (phi), A051953 (cototient).
%K nonn
%O 1,3
%A _Wesley Ivan Hurt_, May 03 2021
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