12135070domain: NAppears in sequences10th binomial transform of (1,0,1,0,1,......), A059841.at n=7A081192For n even a(n) = a(n-1) + 10*a(n-2), for n odd a(n) = a(n-3) + 10 a(n-2); with a(1) = 0, a(2) = 1.at n=15A161999