Number of (n+1) X (n+1) -3..3 symmetric matrices with every 2 X 2 subblock having sum zero and one or three distinct values.

A211324

Number of (n+1) X (n+1) -3..3 symmetric matrices with every 2 X 2 subblock having sum zero and one or three distinct values.

Terms

    a(0) =15a(1) =29a(2) =55a(3) =107a(4) =209a(5) =409a(6) =805a(7) =1583a(8) =3127a(9) =6175a(10) =12233a(11) =24241a(12) =48141a(13) =95655a(14) =190343a(15) =378967a(16) =755249a(17) =1505841a(18) =3004341a(19) =5996175a(20) =11972503a(21) =23911631a(22) =47770041a(23) =95451441a(24) =190761021a(25) =381287447a(26) =762198439a(27) =1523777639a(28) =3046559585a(29) =6091487857

External references