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 A290348 #13 Apr 03 2025 23:10:34
%S A290348 1,1,1,1,1,3,3,3,1,5,5,15,15,105,105,105,105,315,315,315,315,3465,
%T A290348 3465,3465,693,9009,3003,3003,3003,5005,5005,5005,5005,85085,17017,
%U A290348 153153,153153,2909907,2909907,14549535
%N A290348 Denominators of the Harary index for the n-halved cube graph.
%H A290348 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HalvedCubeGraph.html">Halved Cube Graph</a>
%H A290348 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HypercubeGraph.html">Hypercube Graph</a>
%F A290348 a(n) = A000265(A330719(n)). - _Thomas Ordowski_, Mar 29 2025
%e A290348 First few terms are 0, 1, 6, 26, 100, 1096/3, 3920/3, 13936/3, 16544, 296256/5, ....
%t A290348 Table[-2^(n - 1) HarmonicNumber[n] - 2^(2 n - 1) Re[LerchPhi[2, 1, n + 1]], {n, 20}] // Denominator
%Y A290348 Cf. A000265, A290347 (numerators), A330719.
%K A290348 nonn,frac
%O A290348 1,6
%A A290348 _Eric W. Weisstein_, Jul 28 2017