%N Conjectured lower bound for the number of spheres of radius 1 that can be packed in a sphere of radius n.
%C The formula was given by David W. Cantrell in a thread "Packing many equal small spheres into a larger sphere" in the newsgroup sci.math on May 29 2006.
%H Hugo Pfoertner, <a href="/A121346/b121346.txt">Table of n, a(n) for n = 2..10000</a>
%H Sen Bai, X. Bai, X. Che, and X. Wei, <a href="https://doi.org/10.1109/TMC.2015.2508805">Maximal Independent Sets in Heterogeneous Wireless Ad Hoc Networks</a>, IEEE Transactions on Mobile Computing (Volume: 15, Issue: 8, Aug. 1 2016), pp. 2023-2033.
%H David W. Cantrell, <a href="https://groups.google.com/g/sci.math/c/Q9OMtGmXNbg/m/a_AnL8wYel8J">Packing many equal small spheres into a large sphere</a>, post in newsgroup sci.math, May 29 2006.
%H WenQi Huang and Liang Yu, <a href="https://doi.ieeecomputersociety.org/10.1109/TrustCom.2011.233">A Quasi Physical Method for the Equal Sphere Packing Problem</a>, in 2011 IEEE 10th International Conference on Trust, Security and Privacy in Computing and Communications.
%F a(n) = floor(K*(1 - 2*d)/d^3 + 1/(2*d^2)), where d=1/n and K = Pi/(3*sqrt(2)).
%Y Cf. A084828 (Maximum number of spheres of radius one that can be packed in a sphere of radius n).
%A _Hugo Pfoertner_, Jul 22 2006