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 A138725 #12 Feb 03 2021 23:12:40 %S A138725 1,3,11,19,37,55,87,119,169,4,12,20,38,56,88,120,170,21,39,57,89,121, %T A138725 171,58,90,122,172,123,173,124,174,125,175,126,176,127,177,128,178, %U A138725 129,179,130,180,131,181,132,182,133,183,134,184 %N A138725 Atomic numbers in the periodic table of the elements, read downwards along 50 columns, up to the 9th period. %C A138725 This finite sequence has 218 members. Atomic numbers > 218 are not members. %C A138725 This sequence assumes simple extrapolation rather than recent research. - _J. Lowell_, Jan 26 2021 %e A138725 ====================================================== %e A138725 ................... STRUCTURE OF .................... %e A138725 ........ THE PERIODIC TABLE OF THE ELEMENTS ......... %e A138725 ................... (50 columns) .................... %e A138725 ====================================================== %e A138725 1) X................................................X %e A138725 2) XX..........................................XXXXXX %e A138725 3) XX..........................................XXXXXX %e A138725 4) XXX................................XXXXXXXXXXXXXXX %e A138725 5) XXX................................XXXXXXXXXXXXXXX %e A138725 6) XXXX..................XXXXXXXXXXXXXXXXXXXXXXXXXXXX %e A138725 7) XXXX..................XXXXXXXXXXXXXXXXXXXXXXXXXXXX %e A138725 8) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX %e A138725 9) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX %e A138725 ====================================================== %Y A138725 Cf. A099955, A134984, A138723, A138724, A138726, A138727. %K A138725 fini,nonn,tabf %O A138725 1,2 %A A138725 _Omar E. Pol_, Mar 26 2008, Jan 25 2009