

A092636


Number of consecutive prime runs of 1 prime congruent to 1 mod 4 below 10^n.


4




OFFSET

1,2


LINKS

Table of n, a(n) for n=1..9.


FORMULA

Generate the prime sequence with primes labeled 1 mod 4 or 3 mod 4. Add count of primes to sequence if just one prime occurs before interruption by a prime congruent to 3 mod 4.


EXAMPLE

a(3)=31 because 31 single primes occur below 10^3, each interrupted in the run by a prime congruent to 3 mod 4.


PROG

(PARI) a(n)=my(p=2, q=3, t); forprime(r=5, nextprime(10^n), if(q%4==1&&p%4==3&&r%4==3, t++); p=q; q=r); t \\ Charles R Greathouse IV, Sep 30 2011


CROSSREFS

Cf. A091318, A092637A092665.
Sequence in context: A260782 A084235 A002469 * A178792 A007197 A247639
Adjacent sequences: A092633 A092634 A092635 * A092637 A092638 A092639


KEYWORD

more,nonn


AUTHOR

Enoch Haga, Mar 02 2004


EXTENSIONS

a(9) from Charles R Greathouse IV, Sep 30 2011


STATUS

approved



