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 A100259 #6 Apr 30 2014 01:27:34 %S A100259 3,-30,105,-1260,3465,-18018,45045,-875160,2078505,-9699690,22309287, %T A100259 -202811700,456326325,-2035917450,4508102925,-158685222960, %U A100259 347123925225,-1511010027450,3273855059475,-28258538408100 %N A100259 Coefficient of x^2 in 2n-th normalized Legendre polynomial. %e A100259 Example: Legendre(12) = (676039x^12 - 1939938x^10 + 2078505x^8 - 1021020x^6 + 225225x^4 - 18018x^2 + 231)/1024, hence a(6) = -18018. - Neven Juric %o A100259 (PARI) a(n) = polcoeff(pollegendre(2*n, x), 2)*2^valuation((2*n)!, 2) \\ _Michel Marcus_, May 29 2013 %Y A100259 3rd column (without zeros) of triangle A100258. %K A100259 sign %O A100259 1,1 %A A100259 _Ralf Stephan_, Nov 13 2004 %E A100259 Definition corrected by Neven Juric, Jan 10 2009