A307117 Numbers x that are equal to lpf(x)*gpf(x)*(lpf(x)+gpf(x))/2, where lpf(x) and gpf(x) are the least and the greatest prime factors of x: A020639 and A006530.

8, 27, 105, 125, 231, 343, 627, 897, 935, 1331, 1581, 1729, 2197, 2465, 2967, 3525, 4123, 4301, 4715, 4913, 5487, 6859, 7035, 7685, 7881, 9717, 10707, 11339, 12167, 14993, 16377, 17353, 17655, 20213, 20915, 23779, 24389, 24765, 25327, 26331, 26765, 29341, 29607

Offset: 1

Author

Alex Ratushnyak, Mar 25 2019

Keywords

• nonn

Comments

This is A307108 with terms such that lpf(x)=gpf(x), that is, with cubes of primes.

Crossrefs

Cf. A000040, A020639, A006530, A307108.

Cf. A262723 is the subsequence with terms such that lpf(x)!=gpf(x), and (lpf(x)+gpf(x))/2 a prime.