9 Nov
2017
9 Nov
'17
2:15 p.m.
As Warren Smith pointed out, there's an additional condition on this sum: ad-bc=1 On Thu, 9 Nov 2017, Tom Duff wrote:
I got this from Dan Piponi (@sigfpe on twitter):
sum (a+b)^-2 (c+d)^-2 (a+b+c+d)^-2 = 1/24
where the sum is over all integers (a,b,c,d) with 1<=a<=b, 1<=c<=d
Paper: Tropical formulae for summation over a part of SL(2, Z) Nikita Kalinin, Mikhail Shkolnikov https://arxiv.org/abs/1711.02089
-- Tom Duff. Eigenvectors.