Number of (n+1)X(n+1) -9..9 symmetric matrices with every 2X2 subblock having sum zero and one, three or four distinct values.
A211555
Number of (n+1)X(n+1) -9..9 symmetric matrices with every 2X2 subblock having sum zero and one, three or four distinct values.
Terms
- a(0) =151a(1) =1211a(2) =9575a(3) =75219a(4) =586879a(5) =4554563a(6) =35183583a(7) =270747747a(8) =2076732739a(9) =15885966079a(10) =121240881187a(11) =923512887871
External references
- oeis: A211555