Timeline for Questions on symmetric Hadamard matrices

9 events

when toggle format	what		by	license	comment
Aug 5 at 1:39	vote	accept	user369335
Aug 14 at 7:09
Jun 25 at 22:53	history	edited	user369335	CC BY-SA 4.0	added 163 characters in body
Jun 14 at 15:05	comment	added	Padraig Ó Catháin		The Paley II construction gives a symmetric Hadamard matrix of order $2q+2$ for any prime power $q\equiv 1 \mod 4$, with trace $0$. A symmetric Bush-type Hadamard matrix can be constructed with order $16n^2$ whenever there is a symmetric Hadamard matrix of order $4n$, these always have trace $16n^2$. It's conjectured that a symmetric Hadamard matrix exists at all orders $4n$ and that a Bush-type matrix exists for all $4n^2$.
Jun 14 at 12:13	history	edited	user369335	CC BY-SA 4.0	added 26 characters in body
Jun 13 at 23:27	comment	added	Max Alekseyev		It got such a matrix by chance. For other square $n$, constructed matrices are either not symmetric or have zero trace.
Jun 13 at 22:34	history	edited	user369335	CC BY-SA 4.0	added 23 characters in body
Jun 13 at 22:33	comment	added	user369335		Wow, SageMath is so powerful! Thanks for your helpful comment! @MaxAlekseyev
Jun 13 at 15:19	comment	added	Max Alekseyev		SageMath constructs a symmetric Hadamard matrix for $n=66^2$ with trace $n$.
Jun 13 at 12:32	history	answered	user369335	CC BY-SA 4.0