103474domain: NAppears in sequencesNumber of (n+1) X (n+1) -3..3 symmetric matrices with every 2 X 2 subblock having sum zero and three distinct values.at n=14A211323Numbers k such that R_(k+2) + 4*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=13A256928