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 A084622 #10 Jan 03 2017 02:32:09
%S A084622 12,13,16,17,18,19,20,21,24,25,28,29,30,31,32,33,36,37,40,41,42,43,44,
%T A084622 48,49,50,51,52,53,54,55,56,57,60,61,64,65,66,67,68,69,70,71,72,73,76,
%U A084622 77,78,79,80,84,85,88,89,90,91,92,93,96,97,100,101,102,103,104,108,109
%N A084622 Numbers n such that f(n) is a strict local extremum for the function f(x) = phi(x) + sigma(x); i.e., either f(n) > f(n-1) and f(n) > f(n+1) or f(n) < f(n-1) and f(n) < f(n+1).
%C A084622 For runs of consecutive strict local extrema (alternating minima/maxima, zigzags) of f, cf. A066923.
%C A084622 A066485 is an analog of the present sequence for the prime gaps function.
%e A084622 16 is a term since f(16) is a local maximum: f(15) = 32, f(16) = 39, f(17) = 34.
%o A084622 (PARI) f(x)=eulerphi(x)+sigma(x)
%o A084622 {locext(n)=local(a,b,c); a=if(n<2,0,f(n-1)); b=f(n); c=f(n+1); if(a<b&&b>c,1,if(a>b&&b<c,-1,0))}
%o A084622 for(n=1,110,if(locext(n)!=0,print1(n,",")))
%Y A084622 Cf. A066485, A066923.
%K A084622 nonn
%O A084622 1,1
%A A084622 _Klaus Brockhaus_, Jun 01 2003