OFFSET
1,3
FORMULA
comp(n(n+1)/2) - comp(n(n-1)/2), where comp(m) = number of composite numbers less than or equal to m.
EXAMPLE
a(5) = 3, among 11,12,13,14,15 there are three composite numbers 12,14 and 15.
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Mar 29 2004
EXTENSIONS
Corrected and extended by Joshua Zucker, May 08 2006
STATUS
approved