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 A324913 #17 Apr 18 2025 09:59:09
%S A324913 2,6,22,54,182,310,1078,2102,5174,9270,29750,46134,144438,242742,
%T A324913 504886,1029174,3126326,4699190,14136374,22524982,47690806,89633846,
%U A324913 274183222,408400950,1079489590,1884795958,4300715062,7521940534,22554326070,31144260662,95568770102
%N A324913 a(n) = Sum_{k=1..n} 2^k * phi(k), where phi is the Euler totient function A000010.
%H A324913 Robert Israel, <a href="/A324913/b324913.txt">Table of n, a(n) for n = 1..3293</a>
%H A324913 Vaclav Kotesovec, <a href="/A324913/a324913.jpg">Plot of a(n)/(n*2^n) for n = 1..100000</a>
%H A324913 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TotientFunction.html">Totient Function</a>
%H A324913 Wikipedia, <a href="http://en.wikipedia.org/wiki/Euler%27s_phi_function">Euler's totient function</a>
%p A324913 ListTools:-PartialSums([seq(2^k * numtheory:-phi(k),k=1..50)]); # _Robert Israel_, Apr 17 2025
%t A324913 Accumulate[Table[2^k*EulerPhi[k], {k, 1, 40}]]
%Y A324913 Cf. A000010, A002088, A306988.
%K A324913 nonn
%O A324913 1,1
%A A324913 _Vaclav Kotesovec_, Mar 18 2019