%I #29 Sep 30 2024 13:06:46
%S 9,17,35,53,85,117
%N Atomic numbers of halogens in the periodic table.
%C The halogens are all on the second rightmost column of the periodic table. (The rightmost column belongs to the noble gases.) - _Alonso del Arte_, Apr 26 2011
%C From _Daniel Forgues_, Jul 12-13 2015, _Luca Khan_, Sep 9 2024: (Start)
%C Halogens: 9: fluorine (F), 17: chlorine (Cl), 35: bromine (Br), 53: iodine (I), 85: astatine (At) and 117: tennessine (Ts). (End)
%D Monica Halka and Brian Nordstrom, Halogens and Noble Gases, Facts On File (2010), Part 1: The Halogens.
%H Bodner Research Web, <a href="http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch10/group7.php">The Chemistry of the Halogens</a>
%H Royal Society of Chemistry, <a href="http://www.rsc.org/periodic-table">Periodic Table</a>, 2015.
%H Wikipedia, <a href="https://en.m.wikipedia.org/wiki/Halogen">Halogen</a>
%F a(1) = 9; a(n) = a(n-1) + 2 * (ceiling(n/2) + 1)^2, 2 <= n <= 6.
%Y Cf. A099955, alkali metals; A099956, alkaline earth metals; A101648, metalloids; A101647, nonmetals (except halogens and noble gases); A018227, noble gases; A101649, poor metals.
%K nonn
%O 1,1
%A _Parthasarathy Nambi_, Sep 19 2004