%I #2 Mar 30 2012 17:33:54
%S 1,2,3,4,5,6,7,8,8,8,1,2,3,4,5,6,7,8
%N Group number of the elements of the n-th column of the periodic table of the elements with 18 columns.
%e Columns of The Periodic Table of the Elements:
%e 1...2...3...4...5...6...7...8...9...10..11..12..13..14..15..16..17..18.
%e A notation convention of the groups is
%e 1A, 2A, 3B, 4B, 5B, 6B, 7B, 8B, 8B, 8B, 1B, 2B, 3A, 4A, 5A, 6A, 7A, 8A.
%e Then the sequence of this entry is formed from the numeric characters: 1, 2, 3, 4, 5, 6, 7, 8, 8, 8, 1, 2, ...
%e Note that the elements, of the 4th period, whose crystals are ferromagnetics (26=Fe=Iron, 27=Co=Cobalt and 28=Ni=Nickel) are in the group 8B.
%Y Cf. A138723, A138724.
%K easy,fini,full,nonn
%O 1,2
%A _Omar E. Pol_, Mar 27 2008