20751

Appears in sequences

• Semiprimes in A056108.at n=24A113527
• a(n) = a(n-1)+floor(a(n-2)/4) with a(0)=3, a(1)=4.at n=49A182230
• G.f. A(x) satisfies A(x) = 1 / ((1 - x) * (1 - 2 * x * A(x^4))).at n=12A390661