A possible candidate for OEIS

[N. J. A. Sloane]

I will add it to the OEIS - it will be A121231
NJAS

> a(n) - n=D7n binary matrices A such that A*^2* is a binary matrix
> 
> a(1) =3D 2
> a(2) =3D 11
> a(3) =3D 172
>   a(4) =3D 6327
> a(5) =3D 474286
> a(6) =3D 67147431
> .....
> Dan Dima