Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and one or three distinct values.
A211815
Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and one or three distinct values.
Terms
- a(0) =189a(1) =435a(2) =881a(3) =1701a(4) =3247a(5) =6081a(6) =11421a(7) =21369a(8) =40139a(9) =75675a(10) =143095a(11) =272447a(12) =519721a(13) =999049a(14) =1922557a(15) =3726521a(16) =7226935a(17) =14102879a(18) =27524803a(19) =53995609a(20) =105915029a(21) =208603523a(22) =410770735a(23) =811441587a(24) =1602540065a(25) =3172707173a(26) =6279776411
External references
- oeis: A211815