2615004domain: NAppears in sequencesa(n) = T(n,n-2), T given by A026568. Also a(n) = number of integer strings s(0), ..., s(n) counted by T, such that s(n) = 2.at n=16A026571a(n) = Sum_{k=0..2n-2} T(n,k) * T(n,k+2), with T given by A026568.at n=7A027279