Number of (n+1) X (n+1) -2..2 symmetric matrices with every 2 X 2 subblock having sum zero and two or three distinct values.
A211115
Number of (n+1) X (n+1) -2..2 symmetric matrices with every 2 X 2 subblock having sum zero and two or three distinct values.
Terms
- a(0) =12a(1) =26a(2) =54a(3) =106a(4) =208a(5) =398a(6) =766a(7) =1458a(8) =2792a(9) =5324a(10) =10206a(11) =19550a(12) =37616a(13) =72446a(14) =140048a(15) =271194a(16) =526792a(17) =1025268a(18) =2000636a(19) =3911284a(20) =7663264a(21) =15040266a(22) =29571962a(23) =58231566a(24) =114837690a(25) =226761020a(26) =448318274a(27) =887305854a(28) =1757921506a(29) =3485905204
External references
- oeis: A211115