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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..20.

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

CROSSREFS

Cf. A093152 A093153 A091295 A091098 A091099.

Sequence in context: A188749 A045589 A245228 * A188869 A014956 A171287

Adjacent sequences:  A093148 A093149 A093150 * A093152 A093153 A093154

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

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Last modified July 23 17:41 EDT 2021. Contains 346259 sequences. (Running on oeis4.)