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 A158279 #11 Apr 25 2019 09:31:08
%S A158279 1,1,1,2,3,2,6,7,7,11,20,14,35,37,36,70,106,77,182
%N A158279 Number of pseudo-symmetric numerical semigroups with Frobenius number 2*n; that is, pseudo-symmetric numerical semigroups for which the largest integer not belonging to them is 2*n.
%H A158279 S. R. Finch, <a href="http://www.people.fas.harvard.edu/~sfinch/">Monoids of natural numbers</a>
%H A158279 S. R. Finch, <a href="/A066062/a066062.pdf">Monoids of natural numbers</a>, March 17, 2009. [Cached copy, with permission of the author]
%H A158279 J. C. Rosales, P. A. Garcia-Sanchez, J. I. Garcia-Garcia and J. A. Jimenez-Madrid, <a href="https://doi.org/10.1016/j.jpaa.2003.10.024">Fundamental gaps in numerical semigroups</a>, Journal of Pure and Applied Algebra 189 (2004) 301-313.
%H A158279 Clayton Cristiano Silva, <a href="http://www.ime.unicamp.br/~ftorres/ENSINO/MONOGRAFIAS/Clayton.pdf">Irreducible Numerical Semigroups</a>, University of Campinas, São Paulo, Brazil (2019).
%F A158279 a(n) = A158206(2*n).
%e A158279 a(3)=1: the unique pseudo-symmetric semigroup with Frobenius number 6=2*3 is generated by {4, 5, 7}.
%Y A158279 Cf. A124506, A158206.
%K A158279 nonn,more
%O A158279 1,4
%A A158279 _Steven Finch_, Mar 15 2009