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A074693 a(1) = 1, a(n) = a(n-1) + phi(a(n-1)).

%I A074693 #23 Oct 07 2020 09:23:29
%S A074693 1,2,3,5,9,15,23,45,69,113,225,345,521,1041,1733,3465,4905,7497,11529,
%T A074693 18009,29097,47817,71577,114777,184761,307881,482841,804573,1212813,
%U A074693 1854333,2993517,4953069,7752429,12826269,21376953,34207353,55027593,91712493,152705493
%N A074693 a(1) = 1, a(n) = a(n-1) + phi(a(n-1)).
%C A074693 Partial sums of A165931. - _Jaroslav Krizek_, Sep 30 2009
%H A074693 Alois P. Heinz, <a href="/A074693/b074693.txt">Table of n, a(n) for n = 1..500</a> (first 300 terms from T. D. Noe)
%F A074693 1 < a(n+1)/a(n) <= 2 . Does limit a(n+1)/a(n) exist ?
%p A074693 a:= proc(n) option remember; `if`(n=1, 1,
%p A074693       numtheory[phi](a(n-1))+a(n-1))
%p A074693     end:
%p A074693 seq(a(n), n=1..50);  # _Alois P. Heinz_, Oct 02 2020
%t A074693 NestList[# + EulerPhi@ # &, 1, 36] (* _Robert G. Wilson v_, Mar 02 2011 *)
%Y A074693 Cf. A000010, A165931.
%K A074693 easy,nonn
%O A074693 1,2
%A A074693 _Benoit Cloitre_, Sep 03 2002