OFFSET
0,2
FORMULA
a(n) ~ 10^n/(n log 10). - Charles R Greathouse IV, Mar 05 2014
For n > 0, a(n) = A267712(n) + 1. - Jon E. Schoenfield, Apr 19 2018
MATHEMATICA
f[n_] := Block[{k = t = 1}, While[s = PrimePi[ 10^(n/k)]; s != 0, t = t + s; k++]; t]; Array[f, 15, 0]
PROG
(PARI) a(n)=sum(k=2, 10^n, isprimepower(k)>0)+1 \\ Charles R Greathouse IV, Mar 05 2014
(PARI) a(n)=sum(e=1, n*log(10)\log(2), primepi(sqrtnint(10^n, e)))+1 \\ Charles R Greathouse IV, Mar 05 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Mar 05 2014
EXTENSIONS
a(15)-a(21) from Charles R Greathouse IV, Mar 05 2014
STATUS
approved