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%I #9 Mar 30 2012 18:52:04
%S 2,4,12,10,8,6,20,18,16,14,38,36,34,32,30,28,26,24,22,56,54,52,50,48,
%T 46,44,42,40,88,86,84,82,80,78,76,74,72,70,68,66,64,62,60,58,120,118,
%U 116,114,112,110,108,106,104,102,100,98,96,94,92,90
%N Even atomic numbers in the Janet table of the PSE, read right to left along rows.
%C In the Janet arrangement, the elements appear in groups of twice 2, twice 8,... twice 2*k^2, and are here right-aligned:
%C ...............................1,.2;
%C ...............................3,.4;
%C .............5,.6,.7,.8,.9,10,11,12;
%C ............13,14,15,16,17,18,19,20;
%C ...28,39.30,31,32,33,34,35,36,37,38;
%C The even numbers in the table are read top-down, right-to-left and entered into the sequence (which, in consequence, is a permutation of the even numbers.)
%H A. Tarantola, <a href="http://www.ipgp.fr/~tarantola/Files/Professional/Mendeleev/">Periodic table of elements (Janet form)</a>
%e Skipping each second (i.e., each odd) element in the table, the result is
%e 2;
%e 4;
%e 12,10,8,6;
%e 20,18,16,14;
%e 38,36,34,32,30,28,..
%e counting down the even numbers restarting at indices provided by A168380.
%Y Cf. A138100, A138101, A168142.
%K nonn,less,tabf
%O 1,1
%A _Paul Curtz_, Nov 23 2009