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%I #9 Jul 28 2017 09:45:40
%S 0,1,6,26,100,1096,3920,13936,16544,296256,1068672,11652352,42658304,
%T 1100471296,4079876096,15205967872,56939270144,642281037824,
%U 2423854317568,9177027411968,34846713511936,1459319692460032,5568939824513024,21297365878571008
%N Numerators of the Harary index for the n-halved cube graph.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/HararyIndex.html">Harary Index</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/HalvedCubeGraph.html">Halved Cube Graph</a>
%F a(n) = -2^(n-1)*HarmonicNumber(n)-2^(2*n-1)*Re(LerchPhi(2,1,n+1)).
%e First few terms are 0, 1, 6, 26, 100, 1096/3, 3920/3, 13936/3, 16544, 296256/5, ....
%t Table[-2^(n - 1) HarmonicNumber[n] - 2^(2 n - 1) Re[LerchPhi[2, 1, n + 1]], {n, 20}] // Numerator
%Y Cf. A290348 (denominators).
%K nonn,frac
%O 1,3
%A _Eric W. Weisstein_, Jul 28 2017
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