Number of (n+1)X(n+1) -8..8 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.

A211469

Number of (n+1)X(n+1) -8..8 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.

Terms

    a(0) =144a(1) =380a(2) =856a(3) =1808a(4) =3706a(5) =7454a(6) =14786a(7) =29300a(8) =57442a(9) =113394a(10) =221676a(11) =437914a(12) =857230a(13) =1698058a(14) =3335170a(15) =6630316a(16) =13078566a(17) =26101324a(18) =51724674a(19) =103628922a(20) =206316160a(21) =414882652a(22) =829705256a(23) =1674253282a(24) =3362428628a(25) =6806756646

External references