1054130domain: NAppears in sequencesa(n) is the index of the smallest triangular number containing exactly n 5's.at n=9A048360a(n) is the smallest value of m such that A002378(m), the m-th oblong number, contains exactly n 1's.at n=8A048531Numbers k such that the k-th triangular number contains only digits {1,5,9}.at n=13A119139