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 A373281 #12 May 30 2024 09:52:55
%S A373281 1,5,25,125,626,3125,15625,78125,390625,1953130,9765625,48828125,
%T A373281 244140625,1220703125,6103515650,30517578125,152587890625,
%U A373281 762939453125,3814697265625,19073486328250,95367431640625,476837158203125,2384185791015625,11920928955078125
%N A373281 Expansion of Sum_{k>=0} x^(5^k) / (1 - 5*x^(5^k)).
%H A373281 Seiichi Manyama, <a href="/A373281/b373281.txt">Table of n, a(n) for n = 1..1000</a>
%F A373281 G.f. A(x) satisfies A(x) = x/(1 - 5*x) + A(x^5).
%F A373281 If n == 0 (mod 5), a(n) = 5^n + a(n/5) otherwise a(n) = 5^n.
%F A373281 a(n) = Sum_{d|n} d * A054662(d).
%o A373281 (PARI) b(n, k) = sumdiv(n, d, (gcd(d, k)==1)*(moebius(d)*k^(n/d)))/(k*n);
%o A373281 a(n, k=5) = sumdiv(n, d, d*b(d, k));
%Y A373281 Cf. A187767, A373279, A373280, A373282, A373283.
%Y A373281 Cf. A000351, A054662, A055457.
%K A373281 nonn
%O A373281 1,2
%A A373281 _Seiichi Manyama_, May 30 2024