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

A211117

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

Terms

    a(0) =12a(1) =30a(2) =72a(3) =174a(4) =422a(5) =1028a(6) =2510a(7) =6134a(8) =14988a(9) =36594a(10) =89250a(11) =217416a(12) =529010a(13) =1285754a(14) =3121904a(15) =7573550a(16) =18358950a(17) =44474532a(18) =107679342a(19) =260584230a(20) =630363356a(21) =1524363938a(22) =3685232642a(23) =8907169352a(24) =21524344338a(25) =52005554058a(26) =125635087296

External references