121621

Properties

Appears in sequences

• Least positive integer multiples of angle x such that their direction cosines form a unit vector: Sum_{k>0} cos(a(k)*x)^2 = 1, where a(1)=1 and x=3.at n=18A080138
• Numbers k such that 10^k + 8*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=9A102945
• Expansion of g^2/(1 - x^3*g), where g = 1+x*g^3 is the g.f. of A001764.at n=8A391123
• Prime numbersat n=11448