Number of (n+1) X (n+1) -4..4 symmetric matrices with every 2 X 2 subblock having sum zero and three distinct values.
A211491
Number of (n+1) X (n+1) -4..4 symmetric matrices with every 2 X 2 subblock having sum zero and three distinct values.
Terms
- a(0) =28a(1) =56a(2) =110a(3) =206a(4) =392a(5) =728a(6) =1372a(7) =2562a(8) =4838a(9) =9126a(10) =17360a(11) =33116a(12) =63572a(13) =122558a(14) =237382a(15) =461802a(16) =901448a(17) =1766496a(18) =3470060a(19) =6838226a(20) =13498502a(21) =26712038a(22) =52921792a(23) =105046092a(24) =208674308a(25) =415112766a(26) =826217510a(27) =1646150186a(28) =3280944632
External references
- oeis: A211491