2097286domain: NAppears in sequencesNumber of 4 X n 0-1 matrices avoiding simultaneously the right angled numbered polyomino patterns (ranpp) (00;1), (01;0), (10;0) and (01;1).at n=21A100316Inverse Moebius transform of the Mersenne numbers: a(n) = Sum_{d|n} (2^d - 1).at n=20A130887