2072640domain: NAppears in sequencesa(n) are solutions of the 2 equations: 7*a(n) +1 = c(n)^2 and 9*a(n) + 1 = b(n)^2.at n=3A159679Number of isomorphism classes of connected (D_4)-fold coverings of a connected graph with circuit rank n.at n=7A160873a(n) = ((2^b-1)/phi(n))*Sum_{d|n} Moebius(n/d)*d^(b-1) for b = 8.at n=3A160913