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 A137508 #5 Nov 11 2021 16:57:26 %S A137508 2,2,2,8,2,2,8,8,2,2,8,18,8,2,2,8,18,18,8,2,2,8,18,32,18,8,2 %N A137508 Successive structures of alkaline earth metals (periodic table elements from 2nd column). %C A137508 Apparently a(n) = A168281(n+1). - _Georg Fischer_, Nov 11 2021 %e A137508 27 terms: 2, 2 for beryllium, ... Every structure is palindromic (even and odd mixed). Also 2*A106314. %Y A137508 Cf. A005993, A099956, A168281. Same numbers as in A093907. %K A137508 nonn %O A137508 1,1 %A A137508 _Paul Curtz_, Apr 23 2008