244294domain: NAppears in sequencesNumbers k that are the products of two distinct primes such that 2*k-1, 4*k-3, 8*k-7, 16*k-15, 32*k-31, 64*k-63 and 128*k-127 are also products of two distinct primes.at n=25A177216Number of even permutations p of {1,...,n} such that p(i) is not i or i+1.at n=10A293042