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 A054613 #16 Apr 17 2021 01:26:25
%S A054613 0,6,42,228,1344,7800,46956,279972,1681008,10078164,60474120,
%T A054613 362797116,2176832112,13060694088,78364444284,470185001040,
%U A054613 2821111589856,16926659444832,101559966840108,609359740010604,3656158500550080
%N A054613 a(n) = Sum_{d|n} phi(d)*6^(n/d).
%H A054613 Seiichi Manyama, <a href="/A054613/b054613.txt">Table of n, a(n) for n = 0..1285</a>
%F A054613 a(n) = n * A054625(n).
%F A054613 a(n) = Sum_{k=1..n} 6^gcd(n,k). - _Ilya Gutkovskiy_, Apr 16 2021
%o A054613 (PARI) a(n) = if(n==0, 0, sumdiv(n, d, eulerphi(d)*6^(n/d))); \\ _Altug Alkan_, Mar 16 2018
%Y A054613 Column k=6 of A185651.
%Y A054613 Cf. A054625.
%K A054613 nonn
%O A054613 0,2
%A A054613 _N. J. A. Sloane_, Apr 16 2000