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 A054612 #22 Sep 02 2025 14:08:55
%S A054612 0,5,30,135,660,3145,15810,78155,391320,1953405,9768870,48828175,
%T A054612 244157820,1220703185,6103593930,30517584915,152588282640,
%U A054612 762939453205,3814699250430,19073486328215,95367441415140,476837158360185,2384185839844050,11920928955078235,59604645020345640
%N A054612 a(n) = Sum_{d|n} phi(d)*5^(n/d).
%H A054612 Seiichi Manyama, <a href="/A054612/b054612.txt">Table of n, a(n) for n = 0..1430</a>
%F A054612 a(n) = Sum_{k=1..n} 5^gcd(n,k). - _Ilya Gutkovskiy_, Apr 16 2021
%t A054612 a[n_]:= Sum[5^GCD[n,k],{k,n}]; Array[a,30,0] (* _Stefano Spezia_, Sep 02 2025 *)
%o A054612 (PARI) a(n) = if (n, sumdiv(n, d, eulerphi(d)*5^(n/d)), 0); \\ _Michel Marcus_, Apr 16 2021
%Y A054612 Column k=5 of A185651.
%Y A054612 Cf. A001869.
%K A054612 nonn,changed
%O A054612 0,2
%A A054612 _N. J. A. Sloane_, Apr 16 2000