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%I #10 Sep 30 2019 04:04:29
%S 1484,2534,3002,3674,3926,4454,4484,4784,4844,5264,5312,5984,6104,
%T 7994,8294,8414,8774,8834,9074,9164,9944,10004,10724,11024,11684,
%U 11894,12254,13034,13064,13166,13454,13754,14234,15344,15554,16184,16214,16814,17384,17534
%N Numbers k such that phi(k) < phi(k+1) < phi(k+2) < phi(k+3) where phi is the Euler totient function (A000010).
%D Jean-Marie De Koninck, Those Fascinating Numbers, American Mathematical Society, 2009, p. 34, entry 105 and p. 130, entry 1484.
%H Amiram Eldar, <a href="/A327880/b327880.txt">Table of n, a(n) for n = 1..10000</a>
%e 1484 is in the sequence since phi(1484) = 624, phi(1485) = 720, phi(1486) = 742, and phi(1487) = 1486, and 624 < 720 < 742 < 1486.
%t aQ[n_] := AllTrue[Differences @ EulerPhi[n + Range[0, 3]], # > 0 &]; Select[Range[18000], aQ]
%o (PARI) ok(k)={for(i=0, 2, if(eulerphi(k+i) >= eulerphi(k+i+1), return(0))); 1}
%o { select(ok, [1..20000]) } \\ _Andrew Howroyd_, Sep 28 2019
%Y Cf. A000010, A078776, A161962.
%K nonn
%O 1,1
%A _Amiram Eldar_, Sep 28 2019
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