197161domain: NPropertiesPrimalityPrimeyesAppears in sequencesPrimes of the form 16*m^2 + 25, m=1,3,5,...at n=23A087856a(n) is the smallest number k such that with x(1) = k and x(i+1) = 2*x(i) + 1, x(i+1) has exactly one more prime factor (counted with multiplicity) than x(i) for i = 1 to n but not i = n + 1.at n=4A381502Prime numbersat n=17750