423324672domain: NAppears in sequencesa(n) = 2*(a(n-1) + a(n-2)), a(0) = 0, a(1) = 1.at n=21A002605a(n)*a(n+3) - a(n+1)*a(n+2) = 2^n, given a(0)=1, a(1)=1, a(2)=6.at n=20A080879a(n) = Sum_{k=0..n} binomial(2n+1, 2k)*3^(n-k).at n=10A102591