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 A034754 #26 May 07 2021 00:57:04
%S A034754 1,4,11,32,85,260,735,2224,6585,19780,59059,177472,531453,1595076,
%T A034754 4783175,14351168,43046737,129147252,387420507,1162281440,3486785925,
%U A034754 10460412292,31381059631,94143360944,282429536825,847289140932
%N A034754 Dirichlet convolution of 3^(n-1) with phi(n).
%H A034754 Seiichi Manyama, <a href="/A034754/b034754.txt">Table of n, a(n) for n = 1..2096</a>
%F A034754 a(n) ~ 3^(n-1). - _Vaclav Kotesovec_, Sep 11 2019
%F A034754 G.f.: Sum_{k>=1} phi(k) * x^k / (1 - 3*x^k). - _Ilya Gutkovskiy_, Feb 14 2020
%F A034754 a(n) = Sum_{k=1..n} 3^(gcd(k, n) - 1) = A054610(n)/3. - _Seiichi Manyama_, Apr 17 2021
%F A034754 a(n) = Sum_{k=1..n} 3^(n/gcd(n,k) - 1)*phi(gcd(n,k))/phi(n/gcd(n,k)). - _Richard L. Ollerton_, May 06 2021
%t A034754 Table[Sum[3^(n/d - 1)*EulerPhi[d], {d, Divisors[n]}], {n, 1, 30}] (* _Vaclav Kotesovec_, Sep 10 2019 *)
%o A034754 (PARI) a(n) = sum(k=1, n, 3^(gcd(k, n)-1)); \\ _Seiichi Manyama_, Apr 17 2021
%o A034754 (PARI) a(n) = sumdiv(n, d, eulerphi(n/d)*3^(d-1)); \\ _Seiichi Manyama_, Apr 17 2021
%o A034754 (PARI) my(N=40, x='x+O('x^N)); Vec(sum(k=1, N, eulerphi(k)*x^k/(1-3*x^k))) \\ _Seiichi Manyama_, Apr 17 2021
%Y A034754 Cf. A000010, A001867, A034738, A054610.
%K A034754 nonn
%O A034754 1,2
%A A034754 _Erich Friedman_