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

A211114

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

Terms

    a(0) =9a(1) =19a(2) =39a(3) =81a(4) =167a(5) =341a(6) =695a(7) =1405a(8) =2839a(9) =5709a(10) =11479a(11) =23021a(12) =46167a(13) =92461a(14) =185175a(15) =370605a(16) =741719a(17) =1483949a(18) =2968919a(19) =5938861a(20) =11879767a(21) =23761581a(22) =47527255a(23) =95058605a(24) =190125399a(25) =380258989a(26) =760534359a(27) =1521085101a(28) =3042202967a(29) =6084438701

External references