51872

Appears in sequences

• Pairs (x, y), x < y, of f-amicable numbers where f(k) = floor(|k*sin(k)|) sorted by increasing y, then increasing x; f-amicable numbers are defined in A066511.at n=16A066573
• Expansion of (eta(q^3)eta(q^15)/(eta(q)eta(q^5)))^2 in powers of q.at n=26A093065
• Numbers k such that 10^k - 1000000001 is prime.at n=28A273679