84061domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumber of permutations of length n which avoid the patterns 231, 12354.at n=12A116850G.f. satisfies A(x) = ( 1 + x*A(x)^2 / (1 - x*A(x))^2 )^2.at n=6A365148Prime numbersat n=8196