Number of (n+1) X (n+1) -7..7 symmetric matrices with every 2 X 2 subblock having sum zero and three distinct values.
A211442
Number of (n+1) X (n+1) -7..7 symmetric matrices with every 2 X 2 subblock having sum zero and three distinct values.
Terms
- a(0) =90a(1) =188a(2) =356a(3) =654a(4) =1190a(5) =2144a(6) =3882a(7) =7028a(8) =12822a(9) =23490a(10) =43364a(11) =80516a(12) =150510a(13) =283054a(14) =535322a(15) =1018120a(16) =1945094a(17) =3734306a(18) =7194586a(19) =13918418a(20) =26998652a(21) =52549144a(22) =102488144a(23) =200438252a(24) =392604464a(25) =770735354a(26) =1514821088a(27) =2982729598
External references
- oeis: A211442