77079domain: NAppears in sequencesNumbers n such that 249*2^n-1 is prime.at n=20A050883T(n,k)=number of nXk binary matrices with rows and columns in lexicographically strictly increasing order.at n=49A180984T(n,k)=number of nXk binary matrices with rows and columns in lexicographically strictly increasing order.at n=50A180984