A160048 Numerator of the Harary number for the path graph P_n.

0, 2, 5, 26, 77, 87, 223, 962, 4609, 4861, 55991, 58301, 785633, 811373, 835397, 3431678, 29889983, 30570663, 197698279, 201578155, 41054655, 13920029, 325333835, 990874363, 25128807667, 25472027467, 232222818803, 235091155703

Offset: 1

Author

Eric W. Weisstein, Apr 30 2009

Keywords

• nonn
• frac

Examples

			0, 2, 5, 26/3, 77/6, 87/5, 223/10, 962/35, 4609/140, 4861/126, ...
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..200
• Eric Weisstein's World of Mathematics, Harary Index

Crossrefs

Cf. A160049, A027612.

Programs

PARI

harmonic(n)=sum(k=1,n,1/k);
a(n)=numerator(2*n*(harmonic(n)-1)); \\ Andrew Howroyd, Oct 31 2017