login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; text; internal format)
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, A092637-A092665.

Sequence in context: A084235 A288688 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified July 22 18:10 EDT 2017. Contains 289671 sequences.