OFFSET
1,1
COMMENTS
The preliminary sequence begins 2,3,5,7,3*e,13,5*e,19,7*e,3*e^2,31,...
with terms of the form p*e^k, where p is prime, k>=0.
FORMULA
If A(n)is the number of terms not exceeding n, then heuristically A(n)~pi(n). Practically, an approximation is given by formula A(n) ~ n/log(n*log(n)).
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Oct 14 2012
EXTENSIONS
Terms a(1)-a(20) confirmed and terms a(21)-a(46) added by John W. Layman, Oct 24 2012
STATUS
approved