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A093151
Number of odd composites 1 mod 4 less than 10^n.
2
1, 13, 169, 1890, 20216, 210824, 2167819, 22119495, 224576508, 2272476724, 22940979719, 231196075659, 2326967290816, 23397529216327, 235077715264515, 2360380831212204, 23688221424314913, 237630022857420415, 2382971166402199310, 23889590198849417292
OFFSET
1,2
FORMULA
Count odd composites 1 mod 4 less than 10^n
For n>1, a(n) = 25*10^(n-2) - 1 - A091098(n). - Max Alekseyev, May 30 2007
EXAMPLE
Below 10^2 there are 13 odd composites so a(2)=13
KEYWORD
nonn
AUTHOR
Enoch Haga, Mar 24 2004
EXTENSIONS
More terms from Max Alekseyev, May 30 2007
Extended by Max Alekseyev, Oct 13 2009
STATUS
approved