Number of (n+1)X(n+1) -5..5 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.
A211332
Number of (n+1)X(n+1) -5..5 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.
Terms
- a(0) =60a(1) =144a(2) =312a(3) =630a(4) =1266a(5) =2474a(6) =4864a(7) =9466a(8) =18544a(9) =36252a(10) =71260a(11) =140314a(12) =277456a(13) =550506a(14) =1095678a(15) =2189478a(16) =4384860a(17) =8817146a(18) =17756308a(19) =35895256a(20) =72635652a(21) =147493822a(22) =299688524a(23) =610819886a(24) =1245448294a(25) =2546376998a(26) =5207461228
External references
- oeis: A211332