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 A326817 #20 Nov 25 2019 03:30:37 %S A326817 823,943,3133,4387,4873,5443,5563,5863,7213,7753,7873,8383,9007,10333, %T A326817 10693,11113,11503,12043,12763,13483,13843,13921,14623,14683,16573, %U A326817 16663,16963,16993,17113,17983,19003,19093,19303,20083,20143,20953,21613,21733,22513 %N A326817 Numbers k such that phi(k) > phi(k+1) > phi(k+2) > phi(k+3) where phi is the Euler totient function (A000010). %D A326817 Jean-Marie De Koninck, Those Fascinating Numbers, American Mathematical Society, 2009, page 106, entry 823. %H A326817 Amiram Eldar, <a href="/A326817/b326817.txt">Table of n, a(n) for n = 1..10000</a> %e A326817 823 is in the sequence since phi(823) = 822, phi(824) = 408, phi(825) = 400, phi(826) = 348, and 822 > 408 > 400 > 348. %t A326817 aQ[n_] := AllTrue[Differences @ EulerPhi[n + Range[0, 3]], # < 0 &]; Select[Range[23000], aQ] (* _Amiram Eldar_, Oct 20 2019 *) %Y A326817 Cf. A000010, A078776, A161962, A161963, A206581, A327880. %Y A326817 Subsequence of A328056. %K A326817 nonn %O A326817 1,1 %A A326817 _Kritsada Moomuang_, Oct 20 2019