OFFSET
1,2
COMMENTS
Prime powers are defined as numbers of the form p^k with p prime and k >= 1 (A246655).
EXAMPLE
a(1)=1 because the interval [2,2] contains 1 prime power: 2.
a(2)=2 because the interval [3,4] contains 2 prime powers: 3 and 4=2^2.
a(3)=3 because the prime powers in [5,8] are 5, 7, and 8=2^3.
PROG
(PARI) a(n) = sum(k=2^(n-1)+1, 2^n, isprimepower(k) != 0); \\ Michel Marcus, May 17 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Jon E. Schoenfield, May 13 2018
STATUS
approved