90211

Appears in sequences

• Numbers k such that 6*10^k + R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=22A056717
• Consider the recurrence d(k) = (d(k-3)*d(k-2) + 1)/(d(k-5)*d(k-4)*d(k-3)^2*d(k-2)^2*d(k-1)), with d(0..4) = {1,1,1,2,1}. a(n) = numerator(d(2*n+1)).at n=7A377264