Number of (n+1)X(n+1) -9..9 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.
A211552
Number of (n+1)X(n+1) -9..9 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.
Terms
- a(0) =180a(1) =504a(2) =1148a(3) =2508a(4) =5202a(5) =10762a(6) =21622a(7) =43984a(8) =87406a(9) =177030a(10) =351096a(11) =711810a(12) =1414930a(13) =2878790a(14) =5747458a(15) =11748876a(16) =23580200a(17) =48449984a(18) =97774376a(19) =201923574a(20) =409657252a(21) =850120676a(22) =1733171824a(23) =3612646782a(24) =7397620764a(25) =15481145862
External references
- oeis: A211552