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.

1, 1, 1, 2, 3, 2, 6, 7, 7, 11, 20, 14, 35, 37, 36, 70, 106, 77, 182

Offset

1,4

Links

Table of n, a(n) for n=1..19.

S. R. Finch, Monoids of natural numbers

S. R. Finch, Monoids of natural numbers, March 17, 2009. [Cached copy, with permission of the author]

J. C. Rosales, P. A. Garcia-Sanchez, J. I. Garcia-Garcia and J. A. Jimenez-Madrid, Fundamental gaps in numerical semigroups, Journal of Pure and Applied Algebra 189 (2004) 301-313.

Clayton Cristiano Silva, Irreducible Numerical Semigroups, University of Campinas, São Paulo, Brazil (2019).

Formula

a(n) = A158206(2*n).

Example

a(3)=1: the unique pseudo-symmetric semigroup with Frobenius number 6=2*3 is generated by {4, 5, 7}.

Crossrefs

Cf. A124506, A158206.

Sequence in context: A276125 A208611 A209582 * A153984 A025502 A110777

Adjacent sequences: A158276 A158277 A158278 * A158280 A158281 A158282

Keyword

nonn,more

Author

Steven Finch, Mar 15 2009

Status

approved