A139007 - cp's OEIS frontend

A139007 Number of n X n symmetric binary matrices containing no more than two 1s in any 2 X 2 sub-block.

n	a(n)
0	1
1	2
2	5
3	25
4	205
5	2849
6	66677
7	2633485
8	175143651
9	19638725775
10	3710411382331
11	1181447019186469
12	633957805831439213
13	573281808520220290885
14	873645764409736229092874
15	2243689725607702437916265557

[1, 2, 5, 25, 205, 2849, 66677, 2633485, 175143651, 19638725775, 3710411382331, 1181447019186469, 633957805831439213, 573281808520220290885, 873645764409736229092874, 2243689725607702437916265557]

cp's OEIS Frontend

A139007 Number of n X n symmetric binary matrices containing no more than two 1s in any 2 X 2 sub-block.

Table of values

List of values