81969domain: NAppears in sequencesNumbers k such that k and k^2 use only the digits 1, 6, 7, 8 and 9.at n=10A137065Expansion of x*(4+5*x-13*x^2-x^3+x^4) / ( (1-x)*(1-10*x^2+x^4) ).at n=9A179934Number of (n+3) X 5 0..2 matrices with each 4 X 4 subblock idempotent.at n=15A224722