156808domain: NAppears in sequencesG.f.: Product_{n>=1} (1 - A002203(n)*x^n + (-x^2)^n) / (1 + A002203(n)*x^n + (-x^2)^n) where A002203(n) is the companion Pell numbers.at n=20A204384Number of connected dominating sets in the n-ladder graph.at n=12A291706