cp's OEIS Frontend

A378637 Largest m <= n such that phi(m) divides n, where phi is the Euler totient function (A000010).

%I A378637 #13 Dec 06 2024 11:31:18
%S A378637 1,2,2,4,2,6,2,8,2,6,2,12,2,6,2,16,2,18,2,12,2,6,2,24,2,6,2,12,2,22,2,
%T A378637 32,2,6,2,36,2,6,2,33,2,18,2,23,2,6,2,48,2,22,2,12,2,54,2,30,2,6,2,50,
%U A378637 2,6,2,64,2,46,2,12,2,22,2,72,2,6,2,12,2,18,2,75
%N A378637 Largest m <= n such that phi(m) divides n, where phi is the Euler totient function (A000010).
%H A378637 Paolo Xausa, <a href="/A378637/b378637.txt">Table of n, a(n) for n = 1..10000</a>
%F A378637 a(2*k+1) = 2, for k >= 1.
%t A378637 A378637[n_] := If[OddQ[n] && n > 2, 2, Module[{m = n}, While[!Divisible[n, EulerPhi[m]], m--]; m]];
%t A378637 Array[A378637, 100]
%o A378637 (PARI) a(n) = my(m=n); while (n % eulerphi(m), m--); m; \\ _Michel Marcus_, Dec 05 2024
%Y A378637 Right border of A378636.
%Y A378637 Cf. A000010, A319048, A378641.
%K A378637 nonn,easy
%O A378637 1,2
%A A378637 _Paolo Xausa_, Dec 03 2024