338884domain: NAppears in sequencesa(n) = 20 + floor( (1 + Sum_{j=1..n-1} a(j)) / 2 ).at n=24A120145Negative value of coefficient of x^(n-3) in the characteristic polynomial of a certain n X n integer circulant matrix.at n=11A127408Numbers k such that gcd(2^k + 1, k! - 1) has a prime divisor different from 2*k + 1.at n=2A366824