A290348 Denominators of the Harary index for the n-halved cube graph.

1, 1, 1, 1, 1, 3, 3, 3, 1, 5, 5, 15, 15, 105, 105, 105, 105, 315, 315, 315, 315, 3465, 3465, 3465, 693, 9009, 3003, 3003, 3003, 5005, 5005, 5005, 5005, 85085, 17017, 153153, 153153, 2909907, 2909907, 14549535

Offset: 1

Author

Eric W. Weisstein, Jul 28 2017

Keywords

• nonn
• frac

Examples

			First few terms are 0, 1, 6, 26, 100, 1096/3, 3920/3, 13936/3, 16544, 296256/5, ....
		

Links

• Eric Weisstein's World of Mathematics, Halved Cube Graph
• Eric Weisstein's World of Mathematics, Hypercube Graph

Crossrefs

Cf. A000265, A290347 (numerators), A330719.

Programs

Mathematica

Table[-2^(n - 1) HarmonicNumber[n] - 2^(2 n - 1) Re[LerchPhi[2, 1, n + 1]], {n, 20}] // Denominator

Formula

a(n) = A000265(A330719(n)). - Thomas Ordowski, Mar 29 2025