50930domain: NAppears in sequencesNumber of nonnegative integer 3 X 3 matrices with sum of elements equal to n, up to rotational symmetry.at n=13A054771a(n) = (2/3)*Sum_{i=1..n-1} A000129(i)*3^(n-i).at n=10A193519Lesser of 2 successive tetraprimes (k, k+4) sandwiching three consecutive not squarefree numbers.at n=11A367791