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A092636 Number of consecutive prime runs of 1 prime congruent to 1 mod 4 below 10^n. 4
1, 5, 31, 208, 1555, 12465, 102704, 869060, 7540342, 66571720, 595513442 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..11.

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, A092637-A092665.

Sequence in context: A002469 A296032 A301420 * 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

a(10)-a(11) from Chai Wah Wu, Mar 18 2018

STATUS

approved

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Last modified November 15 13:07 EST 2018. Contains 317238 sequences. (Running on oeis4.)