A093151 Number of odd composites 1 mod 4 less than 10^n.

1, 13, 169, 1890, 20216, 210824, 2167819, 22119495, 224576508, 2272476724, 22940979719, 231196075659, 2326967290816, 23397529216327, 235077715264515, 2360380831212204, 23688221424314913, 237630022857420415, 2382971166402199310, 23889590198849417292

Offset: 1

Author

Enoch Haga, Mar 24 2004

Keywords

• nonn

Examples

			Below 10^2 there are 13 odd composites so a(2)=13
		

Crossrefs

Cf. A093152 A093153 A091295 A091098 A091099.

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

Extensions

More terms from Max Alekseyev, May 30 2007

Extended by Max Alekseyev, Oct 13 2009