199955domain: NAppears in sequencesLet M = 2 X 2 matrix [ 1 2 / 5 4 ]; a(n) = (2,1) entry of M^n.at n=6A092166Numbers k such that the k-th triangular number contains only digits {0,1,9}.at n=19A119048Numbers that are the sum of six fourth powers in exactly nine ways.at n=29A345821