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 A037228 #21 Jul 08 2025 22:05:04
%S A037228 1,0,0,0,1,-1,2,0,2,0,5,-1,6,0,2,2,9,-1,10,0,4,2,13,-1,11,3,9,3,18,-2,
%T A037228 19,5,9,5,13,1,24,6,12,4,27,-1,28,6,10,8,31,1,27,5,17,9,36,2,24,8,20,
%U A037228 12,41,-1,42,12,18,14,30,2,47,13,25,5,50,4,51,15,19,15,39,3,56,10,32,18,59,1,41,19
%N A037228 a(n) = phi(n) - pi(n).
%C A037228 It is known that a(n) >= 0 for n >= 61.
%D A037228 D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, p. 11.
%H A037228 Alois P. Heinz, <a href="/A037228/b037228.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from T. D. Noe)
%t A037228 Table[EulerPhi[n]-PrimePi[n],{n,90}] (* _Harvey P. Dale_, Feb 02 2021 *)
%o A037228 (PARI) a(n) = eulerphi(n) - primepi(n); \\ _Michel Marcus_, Aug 08 2019
%Y A037228 Cf. A000010, A000720, A037171, A037229.
%K A037228 sign
%O A037228 1,7
%A A037228 _N. J. A. Sloane_