41757domain: NAppears in sequencesa(n) is the unique odd positive solution x of 2^n = 7x^2+y^2.at n=31A077020Lucas and Lehmer numbers with parameters (1 +- sqrt(-7))/2.at n=32A107920Row sums of the Riordan array (1-4x+4x^2, x(1-2x)) (A167431).at n=29A167433a(0)=1, a(1)=1; thereafter a(n) = -a(n-1) - 2*a(n-2).at n=30A169998