OFFSET
1,3
COMMENTS
In A091295 the counts are 1 higher. I computed the differences through 10^8 and the rest by extrapolating from A091098 and A091099. In the ranges given, the counts of odd composites less than 10^n are higher 1 mod 4 than 3 mod 4. They are exactly opposite for the primes less than 10^n where 3 mod 4 is higher.
FORMULA
Subtract count of odd composites 3 mod 4 less than 10^n from those 1 mod 4
a(n) = A093151(n) - A093152(n). For n>1, a(n) = A091099(n) - A091098(n) - 1. [From Max Alekseyev, May 17 2009]
EXAMPLE
Below 10^3 there are 169 odd composites 1 mod 4 and 163 odd composites 3 mod 4, so a(3)=169-163=6
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Enoch Haga, Mar 24 2004
EXTENSIONS
More terms from Max Alekseyev, May 17 2009
STATUS
approved