%I #3 Mar 30 2012 18:41:15
%S 209,209,209,213,217,221,225,225,229,233,233,237,237,241,245,249,253,
%T 257,261,265,269,273
%N Number of nucleons in longest known radioactive decay series ending with Lead 209, reversed.
%C The numbers are all == 1 mod 4. The sequence was submitted reversed, as it is open in the past. It is unknown if reversed decay series are finite (the "island of stability" hypothesis).
%H C. Heilman, <a href="http://chemlab.pc.maricopa.edu/periodic/periodic.html">The Pictorial Periodic Table</a>
%F a(n)=A080536(n)+A080540(n).
%Y Cf. A080529, A080530, A080531.
%K nonn,hard
%O 0,1
%A _Ralf Stephan_, Feb 20 2003