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Einar Rødland

Oslo, Norway

Mathematician, did my PhD in algebraic geometry working on mirror symmetry. Worked as a consultant for a number of years doing mostly statistics and data analysis, and then bioinformatics for some year. Now doing IT and data analysis.

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Top Questions
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Top Answers
32
Least prime of the form $38^n+31$
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31
*understanding* covariance vs. contravariance & raising / lowering
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17
Can any analytic function be written as the difference of two monotonically increasing analytic functions?
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17
How to evaluate the derivatives of matrix inverse?
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16
"Could not identify document class." error when trying to count words
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13
Solving functional equation $f(x)^2+f(y)^2=f(x+y)(f(f(x))+f(y))$
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13
Does the wordcount package do a proper wordcount?
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12
The proportion of binary digits of $\sum_{k=1}^\infty \Big\lfloor{\frac{k}{2}\sqrt{p}\Big\rfloor}\cdot2^{-k}$ equal to one, is $> 0.978$ if $p=143$.
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11
Direct proof that the wedge product preserves integral cohomology classes?
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10
Cut a unit stick at $n-1$ random points. Expectation of product of fragment lengths is $\prod\limits_{k=n}^{2n-1}\frac1k$. Why?
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10
Find the terms of the sequence $a_{n+1}=1+n/a_n$ that are natural numbers
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10
count words in latex files with input
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10
Solving the Functional Equation $ f \big( x + y f ( x ) \big) = f ( x ) f ( y ) $
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9
What if the Euler Lagrange equation yields a 'trivial' answer
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8
given that $h$ is differentiable and $h(3x)+h(2x)+h(x) = 0$ for all $x\in\mathbb{R},$ is $h$ necessarily identically zero?
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7
How can I obtain a character count?
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7
Distributing $119$ coins to $120$ thieves
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7
Let $X_1$ and $X_2$ be uniform on $n$-spheres. What is the distribution of $\| X_1+X_2\|$?
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7
Matrix exponential: $e^A\ge 0\iff a_{ij}\ge 0$ when $i\neq j$
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7
Rating system incorporating experience
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7
What type of object is a differential form?
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6
For which integers $a,b$ does $ab-1$ divide $a^3+1$?
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6
Is this combinatorial identity a special case of Saalschutz's theroem?
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6
Photon trapping curve
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6
When can a vector field be rescaled to have constant divergence?
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6
A conjecture on numbers coprime to its Euler's totient function
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6
Solving the recurrence relation $T(n) = T(n-\sqrt n) + 1$
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6
Coefficients of a polynomial also are the roots of the polynomial?
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6
Inequality involving expectation
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5
Which of the following sums is a closer approximate to $e^{-5}$?
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