2806565

Appears in sequences

• Numerator of sum(1/(phi(k)sigma(k)),k=1..n), where phi(k) is the totient function and sigma(k) is the sum of the divisors function.at n=18A104526
• a(0) = 0; a(n+1) = 2*a(n) + k where k = 0 if prime(n+2)/prime(n+1) < prime(n+1)/prime(n), otherwise k = 1.at n=22A215410