297544domain: NAppears in sequencesStarting positions of strings of four 3's in the decimal expansion of Pi.at n=30A083611Number of Sophie Germain primes less than 2^n.at n=25A211397a(n) = Sum_{k=0..n} 4^(n-k) * binomial(n-1,n-k) * binomial(2*k,k).at n=7A360319