297073domain: NAppears in sequencesa(0)=1, a(1)=6, a(n) = sum_{k=0}^{k=n-1} 6^k a(k).at n=4A015492a(n) = a(n-1) + a(n-3) + a(n-4), where a(0) = 2, a(1) = 2, a(2) = 2, a(3) = 1.at n=27A295691Numbers n=2*k-1 where Sum_{j=1..k} (-1)^(j+1) * d(2*j-1) achieves a new record, with d(n) = number of divisors of n (A000005).at n=34A318737