89408

Appears in sequences

• Numbers k such that the k-th triangular number contains only digits {3,6,9}.at n=9A119199
• Numbers n such that denominator(sigma(sigma(n))/n) = denominator(sigma(sigma(s))/s) where s = sigma(n).at n=20A275321
• a(n) = A000041(n)*A000070(n-1), n >= 1.at n=14A340492