 # Mark Fischler

Warrenville, IL

I used to be a theoretical physicist, doing very early supergravity work as the first grad student of Peter vanNieuwenhuizen. I had a long career at the Fermi National Accelerator Laboratory, but have moved on to doing defense-related aeronautics work.

But mathematics has always been my strongest suit.

My Erdos number is 4.

Top Questions
52 votes

## Prove that $\sum_{n=1}^\infty \frac{n!}{n^n}$is irrational.

asked Mar 11 '15 at 20:42

14 votes

## If $a+b+c = 3abc$ and $\frac17 \leq k \leq 7$ prove $\frac1{ka+b}+\frac1{kb+c}+\frac1{kc+a} \leq \frac3{k+1}$

asked Mar 22 '17 at 21:25

11 votes

10 votes

## Limits of functions that can't be attacked by Taylor series or L'hopital's rule

asked Sep 12 '16 at 21:31

9 votes

## Is there a clean non-contrived theorem that can only be proven by contradiction?

asked Jul 7 '16 at 23:58

9 votes

9 votes

## Is it well known that for the Pythagorean spiral, $\sum_1^\infty\frac1{a_n+1} = \frac12$?

asked Aug 29 '17 at 21:18

8 votes

## Prove closed form for $\sum_{n\in\Bbb N}\frac1{5n(5n-1)}$

asked Mar 11 at 17:08

8 votes

## A fierce differential-delay equation: df/dx = f(f(x))

asked Jun 4 '14 at 0:11

8 votes

## Are all nimbers included in the surreals?

asked Mar 8 '16 at 0:17