User:Frederik Ravn Klausen

I am a Master's student in mathematics at the University of Copenhagen. I am interested in number theory, combinatorics and mathematical physics.

From A261009: "Comment from Jean-Paul Allouche, Oct 25 2015: As mentioned by Holdum et al. (2005) the following problem, cited in "Concrete Mathematics" by Graham, Knuth, and Patashnik (1994), is still open: prove that for all n > 256, binomial(2n,n) is either divisible by 4 or by 9 (cf. A000984). This can be easily reduced to show that, for all k >= 9, 2*a(k) - a(k+1) >= 4. This has been proved up to huge values of k (Holdum et al. mention k = 10^{13}). "

I am offering 50$ to anyone who proves this!