Number of (n+1) X (n+1) -4..4 symmetric matrices with every 2 X 2 subblock having sum zero and one or three distinct values.

A211492

Number of (n+1) X (n+1) -4..4 symmetric matrices with every 2 X 2 subblock having sum zero and one or three distinct values.

Terms

    a(0) =29a(1) =65a(2) =139a(3) =287a(4) =593a(5) =1189a(6) =2397a(7) =4755a(8) =9475a(9) =18743a(10) =37193a(11) =73609a(12) =145989a(13) =289407a(14) =574531a(15) =1141067a(16) =2268401a(17) =4512781a(18) =8983437a(19) =17896131a(20) =35666275a(21) =71126615a(22) =141881945a(23) =283168249a(24) =565251477a(25) =1128785439a(26) =2254414051a(27) =4503880043

External references