This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A327880 #10 Sep 30 2019 04:04:29 %S A327880 1484,2534,3002,3674,3926,4454,4484,4784,4844,5264,5312,5984,6104, %T A327880 7994,8294,8414,8774,8834,9074,9164,9944,10004,10724,11024,11684, %U A327880 11894,12254,13034,13064,13166,13454,13754,14234,15344,15554,16184,16214,16814,17384,17534 %N A327880 Numbers k such that phi(k) < phi(k+1) < phi(k+2) < phi(k+3) where phi is the Euler totient function (A000010). %D A327880 Jean-Marie De Koninck, Those Fascinating Numbers, American Mathematical Society, 2009, p. 34, entry 105 and p. 130, entry 1484. %H A327880 Amiram Eldar, <a href="/A327880/b327880.txt">Table of n, a(n) for n = 1..10000</a> %e A327880 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 A327880 aQ[n_] := AllTrue[Differences @ EulerPhi[n + Range[0, 3]], # > 0 &]; Select[Range[18000], aQ] %o A327880 (PARI) ok(k)={for(i=0, 2, if(eulerphi(k+i) >= eulerphi(k+i+1), return(0))); 1} %o A327880 { select(ok, [1..20000]) } \\ _Andrew Howroyd_, Sep 28 2019 %Y A327880 Cf. A000010, A078776, A161962. %K A327880 nonn %O A327880 1,1 %A A327880 _Amiram Eldar_, Sep 28 2019