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 A161963 #28 Sep 08 2022 08:45:46 %S A161963 314,524,734,824,944,974,1154,1364,1574,1754,1784,1814,1994,2144,2414, %T A161963 2474,2624,2804,3044,3134,3254,3314,3464,3704,3884,4094,4124,4304, %U A161963 4388,4514,4724,4874,4934,5114,5144,5354,5444,5564,5774,5864 %N A161963 Even numbers n for which phi(n) > phi(n+1). %C A161963 If n is even then for obvious reasons phi(n) will usually be less than or equal to phi(n+1). These are the first few exceptions. %C A161963 Observation based upon calculation: More than 95% of the terms of this sequence have the final digit of 4 for n <= 10^7.. - _Harvey P. Dale_, Jul 24 2012 %H A161963 G. C. Greubel, <a href="/A161963/b161963.txt">Table of n, a(n) for n = 1..5000</a> (terms 1..1000 from T. D. Noe) %F A161963 a(n) = 2 * A001837(n) (follows from the definition). - _Chris Boyd_, Mar 15 2014 %e A161963 314 is in the list because phi(314)=156 and phi(315)=144. %t A161963 Select[2*Range[3000],EulerPhi[#]>EulerPhi[#+1]&] (* _Harvey P. Dale_, Jul 24 2012 *) %o A161963 (PARI) for(n=1, 6000, if(Mod(n,2)==0 && eulerphi(n) > eulerphi(n+1), print1(n", "))) \\ _G. C. Greubel_, Feb 27 2019 %o A161963 (Magma) [n: n in [1..6000] | (n mod 2 eq 0) and (EulerPhi(n) gt EulerPhi(n+1))]; // _G. C. Greubel_, Feb 27 2019 %o A161963 (Sage) [n for n in (1..6000) if mod(n,2)==0 and euler_phi(n) > euler_phi(n+1)] # _G. C. Greubel_, Feb 27 2019 %Y A161963 Cf. A001837, A161962. %K A161963 easy,nonn %O A161963 1,1 %A A161963 David Angell (angell(AT)maths.unsw.edu.au), Jun 22 2009