bio  website  math.haifa.ac.il/~seva 

location  Israel  
age  52  
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comment 
Differences of consecutive ordered fractional parts
@Clark Kimberling: I expanded my answer a little to address the general case of $h\ne 0$. Does this answer your question? 
Jul 1 
revised 
Differences of consecutive ordered fractional parts
added 545 characters in body 
Jul 1 
comment 
When are the powers of 2 sumfree mod n?
What are the values of $n$ smaller than, say, $100$, with the property in question? What does OEIS say? 
Jun 30 
revised 
Differences of consecutive ordered fractional parts
Typo fixed 
Jun 30 
answered  Differences of consecutive ordered fractional parts 
Jun 1 
awarded  Revival 
May 31 
revised 
When is $1+a+a^2+\dotsb+a^{{\rm ord}_n(a)1}$ divisible by $n$?
deleted 45 characters in body; edited title 
May 30 
answered  When is $1+a+a^2+\dotsb+a^{{\rm ord}_n(a)1}$ divisible by $n$? 
May 28 
revised 
Sumsets and dilates: does $A+\lambda A<A+A$ ever hold?
Just fixing (some) typos 
May 28 
accepted  Sumsets and dilates: does $A+\lambda A<A+A$ ever hold? 
May 28 
revised 
Sumsets and dilates: does $A+\lambda A<A+A$ ever hold?
added 288 characters in body 
May 27 
asked  Sumsets and dilates: does $A+\lambda A<A+A$ ever hold? 
May 26 
comment 
When is $1+a+a^2+\dotsb+a^{{\rm ord}_n(a)1}$ divisible by $n$?
As a very basic observation, you have $S_n(\bar a)=0$ provided that both $a$ and $a1$ are coprime with $n$. 
May 25 
awarded  Necromancer 
May 22 
awarded  Revival 
May 22 
revised 
Minimal “sumset basis” in the discrete linear space $\mathbb F_2^n$
added 39 characters in body 
May 22 
revised 
Minimal “sumset basis” in the discrete linear space $\mathbb F_2^n$
added 23 characters in body; edited tags 
May 22 
answered  Minimal “sumset basis” in the discrete linear space $\mathbb F_2^n$ 
May 7 
awarded  Nice Answer 
May 4 
comment 
Vertex expansion of the Hamming graph
@Gordon Royle: seems you are right about the terminology. The graph in my answer is rather called the lattice graph, or the grid graph. 