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Design theory is the subfield of combinatorics concerning the existence and construction of highly symmetric arrangements. Finite projective planes, latin squares, and Steiner triple systems are examples of designs.

4 votes

Constructing Group Divisible Designs - Algorithms?

There are some implementations available in sagemath, see e.g. http://doc.sagemath.org/html/en/reference/combinat/sage/combinat/designs/group_divisible_designs.html#sage-combinat-designs-group-divisib …
Dima Pasechnik's user avatar
4 votes

Self-complementary block designs

There is an example for $n=6$, a quite exceptional one. It comes from the smallest finite sporadic simple group $G=M_{11}$ of order 7920. $G$ has a permutation representation on 12 points, correspondi …
Dima Pasechnik's user avatar
7 votes
Accepted

Combinatorial designs textbook recommendation

There is a list of references in http://www.maths.qmul.ac.uk/~pjc/design/resources.html#books and http://en.wikipedia.org/wiki/Block_design#References From the latter, I know books by Beth et al (a …
Dima Pasechnik's user avatar
5 votes

Intersecting 4-sets

It looks like the conjecture is very close to be right (i.e. $N$ is an upper bound) for $n\geq 12$, as the linear programming (LP) bound equals $N$ for even $n$ even, $500\geq n\geq 12$. When $n$ is o …
Dima Pasechnik's user avatar
5 votes

Minimally intersecting subsets of fixed size

This is a coding theory question. You want to find a binary constant weight $m$ code with $k$ codewords, and of maximal possible distance. There was a lot of research done on this. For the specific c …
Dima Pasechnik's user avatar