Number of (n+1)X(n+1) -7..7 symmetric matrices with every 2X2 subblock having sum zero and one, two or three distinct values.
A211445
Number of (n+1)X(n+1) -7..7 symmetric matrices with every 2X2 subblock having sum zero and one, two or three distinct values.
Terms
- a(0) =113a(1) =307a(2) =723a(3) =1659a(4) =3681a(5) =8171a(6) =17905a(7) =39605a(8) =87221a(9) =194399a(10) =433363a(11) =977621a(12) =2211117a(13) =5053989a(14) =11592995a(15) =26825177a(16) =62296037a(17) =145661855a(18) =341690587a(19) =805669229a(20) =1904747123a(21) =4520182115a(22) =10749370491a(23) =25632216197a(24) =61218130049
External references
- oeis: A211445