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%I #20 Nov 25 2019 03:29:01
%S 106,166,316,526,586,736,1156,1366,1485,1486,1576,1756,1786,1816,1996,
%T 2146,2206,2416,2476,2535,2536,2806,2836,3003,3004,3046,3316,3466,
%U 3675,3676,3886,3927,3928,4096,4126,4306,4455,4456,4485,4486,4516,4726,4785,4786
%N Numbers k such that phi(k-1) < phi(k) < phi(k+1), where phi is the Euler totient function (A000010).
%D Jean-Marie De Koninck, Those Fascinating Numbers, American Mathematical Society, 2009, page 34, entry 105.
%H Amiram Eldar, <a href="/A078776/b078776.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale)
%e phi(105)=48 < phi(106)=52 < phi(107)=106, so 106 is in the sequence.
%t Flatten[Position[Partition[EulerPhi[Range[5000]],3,1],_?(Min[Differences[ #]]> 0&)]//Quiet]+1 (* _Harvey P. Dale_, Jun 14 2019 *)
%o (PARI) for (n=2,3000, if (eulerphi(n-1)<eulerphi(n) && eulerphi(n)<eulerphi(n+1),print1(n",")))
%Y Cf. A000010.
%K nonn
%O 1,1
%A _Jon Perry_, Jan 09 2003
%E More terms from _Michel Marcus_, Mar 17 2014
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