Number of (n+2) X (n+2) symmetric matrices with nonnegative integer entries, trace 0, with n rows that sum to 2, and 2 rows that sum to 1.

A345132

Number of (n+2) X (n+2) symmetric matrices with nonnegative integer entries, trace 0, with n rows that sum to 2, and 2 rows that sum to 1.

Terms

    a(0) =1a(1) =1a(2) =3a(3) =10a(4) =46a(5) =252a(6) =1642a(7) =12316a(8) =104730a(9) =995122a(10) =10450414a(11) =120192924a(12) =1502537932a(13) =20285580880a(14) =294156077364

External references