A160049 Denominator of the Harary number for the path graph P_n.
1, 1, 1, 3, 6, 5, 10, 35, 140, 126, 1260, 1155, 13860, 12870, 12012, 45045, 360360, 340340, 2042040, 1939938, 369512, 117572, 2586584, 7436429, 178474296, 171609900, 1487285800, 1434168450, 40156716600, 38818159380, 1164544781400
Offset: 1
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
- Eric Weisstein's World of Mathematics, Harmonic Number
Crossrefs
Cf. A160048.
Programs
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PARI
harmonic(n)=sum(k=1,n,1/k); a(n)=denominator(2*n*harmonic(n)); \\ Andrew Howroyd, Oct 31 2017
Comments