2454999domain: NAppears in sequencesa(1)=1, then a(n)=2*a(n-1) if n is prime, a(n)=2*a(n-1)+1 if n not prime.at n=21A118255Numbers whose binary representation shows the distribution of prime numbers up to the n-th prime minus 1, using "0" for primes and "1" for nonprime numbers.at n=8A139102Bisection of A139102.at n=4A139107