This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A138101 #8 Jul 22 2016 03:22:20
%S A138101 3,4,13,14,15,16,17,18,19,20,39,40,41,42,43,44,45,46,47,48,49,50,51,
%T A138101 52,53,54,55,56,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,
%U A138101 105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120
%N A138101 The atomic numbers read along the even-indexed rows of the Janet table of the elements.
%C A138101 The union with A138100 gives the first 120 terms of A000027.
%H A138101 Albert Tarantola, <a href="http://www.ipgp.fr/~tarantola/Files/Professional/Mendeleev/">PSE of Elements (Janet form)</a>.
%H A138101 Anonymous, <a href="http://www.webelements.com/nexus/?q=node/981">Janet periodic table</a>, Web Elements Chemistry Nexus
%e A138101 Starts with 3 and 4 of the 2nd row (Li and Be). Next come 13 to 20 of the 4th row (Al to Ca).
%t A138101 Table[Range[2 Ceiling[n/2]^2] + (# + 1) (3 + 2 #^2 + 4 # - 3 (-1)^#)/12 &[n - 1], {n, 2, 8, 2}] // Flatten (* _Michael De Vlieger_, Jul 21 2016 *)
%Y A138101 Cf. A000027, A138100 (odd-indexed rows), A138509 (Left-step Janet periodic table), A137583, A172002.
%K A138101 nonn,less,fini,full
%O A138101 1,1
%A A138101 _Paul Curtz_, May 03 2008
%E A138101 Edited by _R. J. Mathar_, Oct 07 2009