21815

Appears in sequences

• Numbers k such that 251*2^k+1 is prime.at n=16A032502
• Coefficient of x in the reduction of n-th polynomial at A157751 by x^2->x+1.at n=10A192337
• Numbers m with C(2*m, m) + prime(m) prime, where C(2*m, m) = (2*m)!/(m!)^2.at n=48A236242