56666

Appears in sequences

• Numbers having four 6's in base 10.at n=5A043516
• Beach-Williams Pell numbers of type 2pq (p,q primes).at n=18A212075
• Expansion of g.f. A(x) satisfying A(x)^2 = A(x*A(x)) / (1-x) with A(0) = 0.at n=14A367387