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 A333293 #14 Mar 24 2020 15:35:57
%S A333293 3,14,39,105,191,374,649,1020,1463,2268,3161,4463,6065,7553,9477,
%T A333293 12813,16097,20318,25167,29413,34479,42718,50841,59395,69701,80318,
%U A333293 91583,108061,123435,141450,164057,183139,203277,227225,249701,282119,319757,351005,382057,428477,472681,522094,580283,623943,671519
%N A333293 a(n) = Sum_{k=1..n-1} k^2*phi(k) + n^2*phi(n)/2, where phi = A000010.
%H A333293 Robert Israel, <a href="/A333293/b333293.txt">Table of n, a(n) for n = 2..10000</a>
%p A333293 P:= [seq(k^2*numtheory:-phi(k),k=1..100)]:
%p A333293 T:= ListTools:-PartialSums(P):
%p A333293 seq(T[i-1]+P[i]/2,i=2..100); # _Robert Israel_, Mar 24 2020
%o A333293 (PARI) a(n) = sum(k=1, n-1, k^2*eulerphi(k)) + n^2*eulerphi(n)/2; \\ _Michel Marcus_, Mar 23 2020
%Y A333293 Cf. A319087, A000010.
%Y A333293 Next-to-last diagonal of A333292.
%K A333293 nonn
%O A333293 2,1
%A A333293 _N. J. A. Sloane_, Mar 23 2020