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 A373279 #15 May 30 2024 09:53:10
%S A373279 1,3,10,27,81,246,729,2187,6571,19683,59049,177174,531441,1594323,
%T A373279 4783050,14348907,43046721,129140409,387420489,1162261467,3486785130,
%U A373279 10460353203,31381059609,94143181014,282429536481,847288609443,2541865834900,7625597484987
%N A373279 Expansion of Sum_{k>=0} x^(3^k) / (1 - 3*x^(3^k)).
%H A373279 Seiichi Manyama, <a href="/A373279/b373279.txt">Table of n, a(n) for n = 1..1000</a>
%F A373279 G.f. A(x) satisfies A(x) = x/(1 - 3*x) + A(x^3).
%F A373279 If n == 0 (mod 3), a(n) = 3^n + a(n/3) otherwise a(n) = 3^n.
%F A373279 a(n) = Sum_{d|n} d * A046211(d).
%o A373279 (PARI) b(n, k) = sumdiv(n, d, (gcd(d, k)==1)*(moebius(d)*k^(n/d)))/(k*n);
%o A373279 a(n, k=3) = sumdiv(n, d, d*b(d, k));
%Y A373279 Cf. A187767, A373280, A373281, A373282, A373283.
%Y A373279 Cf. A000244, A046211, A051064, A364222.
%K A373279 nonn
%O A373279 1,2
%A A373279 _Seiichi Manyama_, May 30 2024