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 A099955 #17 Jun 19 2014 11:54:50 %S A099955 1,3,11,19,37,55,87 %N A099955 Atomic numbers in first column in the Mendeleyev periodic table of elements. %C A099955 Atomic numbers of hydrogen and then the alkali metals. %F A099955 a(n) = A018227(n-1) + 1. - _Lekraj Beedassy_, Mar 31 2006 %e A099955 The atomic number of sodium is 11. %Y A099955 Cf. A099956, alkaline earth metals; A101648, metalloids; A101647, nonmetals (except halogens and noble gases); A097478, halogens; A018227, noble gases; A101649, poor metals. %K A099955 nonn,fini,full %O A099955 1,2 %A A099955 _Parthasarathy Nambi_, Nov 12 2004 %E A099955 Edited by _N. J. A. Sloane_ at the suggestion of Lekraj Beedassy, Jan 13 2008