This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A075845 #18 Apr 21 2025 02:26:15 %S A075845 1,2,6,31,286,4600,130664,6619840,591478944,93683332808, %T A075845 26438906945728,13204957909414302,11705869922500953011, %U A075845 18478647155522687153022,51703789444327985876248510,256918480515843999119385185643,2272506643204540750098828441592950 %N A075845 Associated to determinants of skew-symmetric matrices related to Catalan-numbers or central binomial coefficients. %C A075845 Appears to be the Hankel transform of A127632. - _Paul Barry_, Jan 20 2007 %H A075845 Roland Bacher, <a href="http://dx.doi.org/10.5802/jtnb.344">Determinants of matrices related to the Pascal triangle</a>, Journal de Théorie des Nombres de Bordeaux 14 (2002), 19-41. %F A075845 a(n) = sqrt(det(M(2*n))) where M(2*n) is the 2n X 2n matrix with entries defined by m(i,0)=alpha(i), m(0,j)=beta(j), m(i,j) = m(i-1,j)+m(i,j-1) (using indexing 0..2n-1 for rows and columns), alpha = 0, 1, 1, 2, 5, 14, 42, ... = Catalan numbers (A000108) shifted by 1 position and beta(k) = -alpha(k) [from Bacher]. - _Sean A. Irvine_, Mar 10 2025 %Y A075845 Cf. A000108. %K A075845 nonn %O A075845 1,2 %A A075845 _Roland Bacher_, Oct 15 2002 %E A075845 a(17) from _Sean A. Irvine_, Mar 10 2025