Zsbán Ambrus
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Next privilege 250 Rep.
 Apr24 comment Minimum number of real multiplications to multiply two quaternions Also posted to Theoretical Computer Science: cstheory.stackexchange.com/q/31251/8067 Apr22 comment Analogue of Fáry's theorem taking sphere and geodesics instead of plane and straight lines. I guess it's true. Couldn't you draw any graph on the sphere by first drawing it on the plane, then copying the drawing to a very small part of the sphere where the great circle segments are very close to straight lines in the original drawing? Mar20 awarded Commentator Mar20 comment 4 Sided dice - flawed logic? I get 83/128 as the answer, slightly more than you. Mar2 comment Identify subsets of $\mathbb{N}$ with their characteristic functions See also cross-post at mathoverflow.net/q/198807/5340 "Question about of comeager set" Dec20 awarded Caucus Dec16 comment Hölder regularity of the simple layer heat potential (question on the proof) Cross-posted to Mathoverflow, at mathoverflow.net/q/190870/5340 "Question on a proof by Solonnikov,Ladyzhenskaya,Ural'tseva" Jun25 awarded Informed Jun16 awarded Critic Mar8 comment What was the first bit of mathematics that made you realize that math is beautiful? (For children's book) I think it's more impressive that if you subtract one from that number, you get its reciprocial. Oct22 answered Eleven unit squares inside a larger square May15 comment Monochromatic triangles in a two-coloring of the plane This is posed as a difficult problem number 14.8 in Lovász László, Combinatorial Problems and Exercises, 2nd ed. You may check out the hints given there in the hints section. Mar11 comment Number of integer solutions to $3i^2 + 2j^2 = 77 \cdot 6^{2012}$ I don't understand. So what if the ratio $i/j$ is neither 5 nor 5/3? Mar9 comment What makes elementary functions elementary? That definition sounds wrong to me. By that definition, $\sin x = ax + b$ would have an elementary solution $x$ as a function of $a, b$. Mar4 comment Need some help settling a bet Also, in the future, please try to use titles for your posts that help people browsing the titles to decide whether they might be able to help in your question. Eg. here you could use the title “Is there a power of two divisible by three?” or “Splitting pizza to three people evenly by repeatedly halving slices”. Mar4 comment Puzzle: $(\Box @)+(\Box @) = (\Box\bigstar\Box$) @barf: it was probably downvoted because there's an earlier answer that seems complete enough. Mar4 comment How many fours are needed to represent numbers up to $N$? By the way, if you allow logarithms, you don't even need four fours: actually three fours are enough to represent any positive integer like $\log\bigl(\log 4/\log(\surd\surd\dots\surd4)\bigr)/\log 4$. Feb25 answered Convolution of the Möbius function with itself Feb18 awarded Supporter Feb17 awarded Teacher