OFFSET
1,4
COMMENTS
Is this the same as A096620? - R. J. Mathar, Jan 26 2010
Yes, except for offset, because n*(harmonic(n)-harmonic(n-1)) = 1 which is an integer. - Andrew Howroyd, Oct 31 2017
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
EXAMPLE
0, 2, 5, 26/3, 77/6, 87/5, 223/10, 962/35, 4609/140, 4861/126, ...
PROG
(PARI)
harmonic(n)=sum(k=1, n, 1/k);
a(n)=denominator(2*n*harmonic(n)); \\ Andrew Howroyd, Oct 31 2017
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Eric W. Weisstein, Apr 30 2009
STATUS
approved