Number of primes less than 10^n and equal to the difference of two consecutive fifth powers (x+1)^5 - x^5 = 5x(x+1)(x^2+x+1)+1 (A121616). Values of x = A121617. Sequence of number of primes less than 10^n and of the form (x+1)^5 - x^5 have similar characteristics to similar sequences for natural primes (A006880) and cuban primes (A113478).