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The first bisection of the sequence A002616 of reduced totients.
1

%I #18 Jun 20 2017 23:11:45

%S 1,2,3,3,5,6,2,8,9,3,11,10,9,14,15,5,6,18,6,20,21,6,23,21,8,26,10,9,

%T 29,30,3,6,33,11,35,36,10,15,39,27,41,8,14,44,6,15,18,48,15,50,51,6,

%U 53,54,18,56,22,6,24,55,20,50,63,21,65,9,18,68,69,23,30,14,21,74,75,24,30,78,26,33

%N The first bisection of the sequence A002616 of reduced totients.

%C Fixed points n where n=a(n) are n=1, 2, 3, 5, 6, 8, 9, 11,... = A005097.

%C There are pairs of the consecutive terms of the form (3*k,k): 6,2, 9,3, 15,5, 18,6, 33,11, 54,18, 63,21, 69,23, 78,26, ... . It seems that k is the set of all A174100(n), n>1, plus a few exceptions (like the pair 126, 42).

%H G. C. Greubel, <a href="/A185026/b185026.txt">Table of n, a(n) for n = 1..5000</a>

%F a(n) = A002616(2*n+1).

%p A185026 := proc(n)

%p numtheory[lambda](2*n+1)/2 ;

%p end proc: # _R. J. Mathar_, Mar 27 2013

%t Table[ CarmichaelLambda[2*n + 1]/2, {n, 1, 80}] (* _Jean-François Alcover_, Apr 04 2013 *)

%K nonn

%O 1,2

%A _Paul Curtz_, Dec 24 2012