bio  website  math.ubc.ca/~israel 

location  Vancouver BC  
age  63  
visits  member for  3 years, 7 months 
seen  3 hours ago  
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Associate Professor Emeritus, University of British Columbia, and Optimization Algorithms Researcher, DWave Systems, Burnaby BC
12h

awarded  Nice Answer 
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How did the summation operation come into use?
From en.wikipedia.org/wiki/Gnomon : "Hero of Alexandria defined a gnomon as that which, when added to an entity (number or shape), makes a new entity similar to the starting entity. In this sense Theon of Smyrna used it to describe a number which added to a polygonal number produces the next one of the same type." 
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Obscure Names in Mathematics
The Tomato Can principle. 
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Obscure Names in Mathematics
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answered  Obscure Names in Mathematics 
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answered  How did the summation operation come into use? 
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Quantitative stability: Hausdorff distance between subdifferentials
You can easily modify this example to come up with smooth $f$ and $g$ with $\f  g\_\infty$ but $\delta f(0) = \{C\}$ and $\delta g(0) = \{C\}$, $f$ and $g$ being translates of smoothed versions of $C x$. 
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answered  Convergence on a random graph 
Oct 20 
answered  The limit of edgemidpoint convex polyhedra 
Oct 19 
revised 
A generalisation of Narayanalike numbers (walks on the 2D lattice)
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Oct 19 
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A generalisation of Narayanalike numbers (walks on the 2D lattice)
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Oct 19 
revised 
A generalisation of Narayanalike numbers (walks on the 2D lattice)
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Oct 19 
revised 
Unbounded convex not containing a ray  example without using a basis
added 24 characters in body 
Oct 19 
answered  Unbounded convex not containing a ray  example without using a basis 
Oct 15 
answered  Does the Gamma function preserve integers? 
Oct 15 
revised 
Points with pairwise integer distances in the plane
edited body 
Oct 15 
answered  Points with pairwise integer distances in the plane 
Oct 15 
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Sum of n independent F distribution random variables
Yes, using Maple. 
Oct 14 
answered  A generalisation of Narayanalike numbers (walks on the 2D lattice) 
Oct 14 
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Squares sum problem
For sums $\le n$, you want the sequence of partial sums of this sequence, which seems not to be in OEIS (yet). That will have generating function $(1x)^{1} \prod_{m=1}^\infty (1 + x^{m^2})$. 