482435457922domain: NAppears in sequencesa(n) is the rational part of A(n) = (6-sqrt(7))*A(n-1) - (12-4*sqrt(7))*A(n-2) + (8-3*sqrt(7))*A(n-3) with A(0)=3, A(1)=6-sqrt(7), A(2)=19-4*sqrt(7).at n=20A215817