Number of (n+1) X (n+1) -5..5 symmetric matrices with every 2 X 2 subblock having sum zero and three distinct values.

A211330

Number of (n+1) X (n+1) -5..5 symmetric matrices with every 2 X 2 subblock having sum zero and three distinct values.

Terms

    a(0) =46a(1) =90a(2) =172a(3) =316a(4) =588a(5) =1070a(6) =1974a(7) =3608a(8) =6670a(9) =12310a(10) =22930a(11) =42818a(12) =80560a(13) =152240a(14) =289462a(15) =553112a(16) =1062084a(17) =2049116a(18) =3968676a(19) =7718410a(20) =15055782a(21) =29469492a(22) =57813502a(23) =113731682a(24) =224119946a(25) =442604110a(26) =875210760a(27) =1733534748a(28) =3436966638

External references