|
|
A265030
|
|
Numerator of Kirchhoff index of ladder graph L_n.
|
|
1
|
|
|
1, 5, 71, 214, 11725, 6031, 415177, 140972, 1305393, 14793725, 289997917, 57882242, 6527639365, 7542845429, 1833039251, 19332937048, 2753465251825, 337099968813, 53020154848357, 28728290846950, 329717936541119, 1057437743438813, 17980324175708377, 1583743732945924
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
a(n) = numerator of k(n) = (1/3)*n^2*(n-sqrt(3)/tanh(n*log(2-sqrt(3)))). k(n) is also equal to n*(n^2-1)/3 + n*sum(k=0, n-1, 1/(1 + 2*sin(Pi*k/(2*n))^2)). - Altug Alkan, Dec 02 2015
|
|
EXAMPLE
|
1, 5, 71/5, 214/7, 11725/209, 6031/65, 415177/2911, 140972/679, ...
|
|
MATHEMATICA
|
f[n_] := Numerator@ Simplify[(1/3)*n^2*(n - Sqrt[3]/Tanh[n*Log[2 - Sqrt[3]]])]; Array[f, 24] (* Robert G. Wilson v, Dec 02 2015 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,frac
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|