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 A072168 #7 Sep 06 2024 20:15:18 %S A072168 1,1,1,1,3,6,12,27,63,155,401,1086,3067,8995,27340,85905,278484, %T A072168 929713,3191200,11245602,40631627,150342632,569071745,2201355133, %U A072168 8694775794,35035655103,143916920871,602218550964,2565370007348,11118142868084,48994958103507 %N A072168 Floor of ratio of volume of n-dimensional cube of side 2 to volume of n-dimensional ball of radius 1. %D A072168 J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 9. %F A072168 a(n) = floor(2^n * Gamma(n/2+1) / Pi^(n/2)). %Y A072168 Cf. A057649, A072345, A072346. %K A072168 nonn %O A072168 0,5 %A A072168 _N. J. A. Sloane_, Sep 06 2003