login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A302434 Number of primes of the form b^2 + 2 for b <= 10^n. 3
4, 12, 69, 447, 3423, 27869, 236985, 2054022, 18127693, 162237123 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
From Jacques Tramu, Sep 13 2018: (Start)
Table C(i) = a(i)/(n*log(n)), with n = 10^i:
a(1) = 4 C(1) = 0.92103404
a(2) = 12 C(2) = 0.55262042
a(3) = 69 C(3) = 0.47663511
a(4) = 447 C(4) = 0.41170221
a(5) = 3423 C(5) = 0.39408744
a(6) = 27869 C(6) = 0.38502446
a(7) = 236985 C(7) = 0.38197469
a(8) = 2054022 C(8) = 0.37836484
a(9) = 18127693 C(9) = 0.37566500
a(10) = 162237123 C(10) = 0.37356478
(End)
LINKS
EXAMPLE
a(1) = 4 because there are 4 primes of the form b^2+2 for b <= 10: 2, 3, 11 and 83.
PROG
(PARI) {a(n) = sum(k=0, 10^n, isprime(k^2+2))}
CROSSREFS
Number of primes of the form b^2+m for b <= 10^n: A302443 (m=-3), A302442 (m=-2), A206709 (m=1), this sequence (m=2), A302435 (m=3).
Cf. A056899.
Sequence in context: A369284 A358409 A180386 * A121771 A009621 A335907
KEYWORD
nonn,more
AUTHOR
Seiichi Manyama, Apr 07 2018
EXTENSIONS
a(10) from Jacques Tramu, Sep 13 2018
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 21 22:43 EDT 2024. Contains 374478 sequences. (Running on oeis4.)