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 A258434 #19 Sep 08 2022 08:46:12
%S A258434 0,3,7,14,21,34,43,60,75,96,111,140,157,190,217,248,273,318,343,392,
%T A258434 429,474,507,568,605,664,711,772,813,892,931,1008,1069,1140,1201,1284,
%U A258434 1333,1426,1497,1584,1641,1752,1807,1916,2001,2094,2163,2288
%N A258434 n^2 - phi(n).
%F A258434 a(n) = A000290(n) - A000010(n).
%F A258434 For p prime, a(p) = A002061(p); A119959 is a subsequence. - _Michel Marcus_, Jun 06 2015
%e A258434 a(5) = 21, since 5^2 = 25 and phi(5) = 4.
%t A258434 Table[n^2 - EulerPhi[n], {n, 200}]
%o A258434 (PARI) vector(50, n, n^2-eulerphi(n)) \\ _Michel Marcus_, May 30 2015
%o A258434 (Magma) [n^2 - EulerPhi(n): n in [1..60]]; // _Vincenzo Librandi_, Jun 03 2015
%Y A258434 Cf. A000290, A000010.
%K A258434 nonn,easy
%O A258434 1,2
%A A258434 _Carlos Eduardo Olivieri_, May 30 2015