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 A022157 #26 Aug 14 2022 18:07:17
%S A022157 0,0,1,-2,9,4,25,0,27,36,81,0,121,100,97,56,225,108,289,112,249,324,
%T A022157 441,64,445,484,441,352,729,388,841,448,769,900,841,324,1225,1156,
%U A022157 1137,576,1521,996,1681,1216,1161,1764,2025,704,2023,1780
%N A022157 a(n) = n^2 - phi(n)*tau(n)^2.
%C A022157 An example of a sequence constructed from an arithmetic inequality.
%H A022157 T. D. Noe, <a href="/A022157/b022157.txt">Table of n, a(n) for n = 1..2000</a>
%H A022157 S. Porubsky and M. G. Greening, <a href="http://www.jstor.org/stable/2319097">Problem E2351</a>, Amer. Math. Monthly, 80, 1973, p. 436.
%F A022157 a(n) >= 0 for all n except for n = 4.
%F A022157 a(n) = 0 if and only if n is one of 1, 2, 8, 12.
%p A022157 with(numtheory); [ seq(n^2-phi(n)*tau(n)^2,n=1..100) ];
%t A022157 Table[n^2 - EulerPhi[n]DivisorSigma[0, n]^2, {n, 50}] (* _Harvey P. Dale_, Apr 12 2013 *)
%o A022157 (PARI) a(n) = n^2 - eulerphi(n)*numdiv(n)^2; \\ _Michel Marcus_, Jun 21 2017
%o A022157 (Magma) [n^2-EulerPhi(n)*NumberOfDivisors(n)^2: n in [1..60]]; // _Vincenzo Librandi_, Jun 21 2017
%o A022157 (GAP) List([1..50],n->n^2-Phi(n)*Tau(n)^2); # _Muniru A Asiru_, Sep 29 2018
%Y A022157 Cf. A110601.
%K A022157 sign,easy,nice
%O A022157 1,4
%A A022157 _N. J. A. Sloane_