1114560domain: NAppears in sequencesa(n) = [x^n](x - 2*x^3)/(1 - 2*x*(x + 1))^2.at n=13A331319Numbers m such that A034448(A188999(m)) = k*m for some k, where A034448 and A188999 are respectively the unitary and the bi-unitary sigma function.at n=40A369204