600281

Appears in sequences

• Composite numbers whose prime factors contain no digits other than 1 and 4.at n=24A036304
• a(n) is the smallest positive integer k such that d(k) = d(k+2*n) = 2*n, where d(m) (A000005) is the number of positive divisors of m, or 0 if no such k exists.at n=4A139416