

A091295


(Number of primes == 3 mod 4 less than 10^n)  (number of primes == 1 mod 4 less than 10^n).


3



1, 2, 7, 10, 25, 147, 218, 446, 551, 5960, 14252, 63337, 118472, 183457, 951700, 3458334, 6284060, 2581691, 80743228, 259753425
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OFFSET

1,2


REFERENCES

Hans Riesel, Prime Numbers and Computer Methods for Factorization, 2nd ed., Birkhauser, The distribution of primes between the two series 4n+1 and 4n+3, pages 7377, with graphs.


LINKS

Table of n, a(n) for n=1..20.
Marc Deléglise, Pierre Dusart, and XavierFrancois Roblot, Counting primes in residue classes, Math. Comp. 73 (2004), no. 247, 15651575.
Carlos Rivera, Puzzle 256, Jack Brennen old records, The Prime Puzzles & Problems Connection.


FORMULA

a(n) = A091099(n)  A091098(n) = A093153(n) + 1. [Max Alekseyev, May 17 2009]


EXAMPLE

a(1) = 1 because below 10^1 3 and 7 are 3 mod 4 and 5 is 1 mod 4 and the difference is 21=1.


CROSSREFS

Cf. A091098, A091099. A002144, A002145, A091318, A091267.
Sequence in context: A066967 A222450 A032007 * A215407 A084184 A015963
Adjacent sequences: A091292 A091293 A091294 * A091296 A091297 A091298


KEYWORD

nonn,more


AUTHOR

Enoch Haga, Feb 23 2004


EXTENSIONS

a(17)a(20) from Marc Deleglise, Jun 28 2007


STATUS

approved



