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A139795 Least m such that k>=m implies phi(k)>=n (where phi is the Euler totient function, sequence A000010).

%I A139795 #13 Nov 24 2024 11:14:42
%S A139795 1,3,7,7,13,13,19,19,31,31,31,31,43,43,43,43,61,61,61,61,67,67,67,67,
%T A139795 91,91,91,91,91,91,91,91,121,121,121,121,127,127,127,127,151,151,151,
%U A139795 151,151,151,151,151,211,211,211,211,211,211,211,211,211,211,211,211,211
%N A139795 Least m such that k>=m implies phi(k)>=n (where phi is the Euler totient function, sequence A000010).
%C A139795 Define b(n)=A006511(m)+1 where m is the unique integer such that A002202(m)<n<=A002202(m+1) (with the convention A002202(0)=A006511(0)=0). Then a(1)=b(1) and a(n+1)=max(a(n),b(n+1)).
%C A139795 The sequence a(n) without the repetitions is 1+A036913(n).
%H A139795 Max Alekseyev, <a href="/A139795/b139795.txt">Table of n, a(n) for n = 1..10000</a>
%H A139795 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%e A139795 a(5)=13 because if k>=13, then phi(k)>=5, but phi(12)=4.
%o A139795 (PARI) {m=0;for(n=1,100,print1(m+1,",");trap(,0,m=max(m,vecmax(invphi(n)))))}
%Y A139795 Different from A137315 (see Comments in that entry).
%K A139795 nonn
%O A139795 1,2
%A A139795 _Benoit Jubin_, May 21 2008