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Number of odd composites below 10^n that are congruent to 3 modulo 4.
2

%I #11 Oct 08 2013 13:05:36

%S 0,12,163,1881,20192,210678,2167602,22119050,224575958,2272470765,

%T 22940965468,231196012323,2326967172345,23397529032871,

%U 235077714312816,2360380827753871,23688221418030854,237630022854838725,2382971166321456083,23889590198589663868

%N Number of odd composites below 10^n that are congruent to 3 modulo 4.

%F For n>1, a(n) = 25*10^(n-2) - A091099(n) [From _Max Alekseyev_, May 17 2009]

%e Below 10^2 there are 12 odd composites 3 mod 4 so a(2)=12

%Y Cf. A093151 A093153 A091295 A091098 A091099.

%K nonn

%O 1,2

%A _Enoch Haga_, Mar 24 2004

%E a(9) from _Ryan Propper_, Jun 21 2005

%E a(10)-a(20) from _Max Alekseyev_, May 17 2009, Oct 08 2013