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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A216815 Primes congruent to 1 or 9 mod 20. 5
29, 41, 61, 89, 101, 109, 149, 181, 229, 241, 269, 281, 349, 389, 401, 409, 421, 449, 461, 509, 521, 541, 569, 601, 641, 661, 701, 709, 761, 769, 809, 821, 829, 881, 929, 941, 1009, 1021, 1049, 1061, 1069, 1109, 1129, 1181, 1201, 1229, 1249, 1289, 1301, 1321, 1361, 1381, 1409, 1429, 1481, 1489, 1549, 1601, 1609, 1621, 1669, 1709, 1721, 1741, 1789, 1801, 1861 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This is a subset of A033205 but it is an important sequence in its own right.

REFERENCES

David A. Cox, "Primes of the Form x^2 + n y^2", Wiley, 1989; see p. 33.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Prime[Range[300]], MemberQ[{1, 9}, Mod[#, 20]]&] (* Vincenzo Librandi, Mar 22 2013 *)

PROG

(MAGMA) [p: p in PrimesUpTo(2000) | p mod 20 in [1, 9]]; // Vincenzo Librandi, Mar 22 2013

CROSSREFS

A subset of A033205. Cf. A216816.

Sequence in context: A069454 A035789 A080899 * A157141 A107218 A058900

Adjacent sequences:  A216812 A216813 A216814 * A216816 A216817 A216818

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Sep 20 2012

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 19 03:34 EDT 2019. Contains 328211 sequences. (Running on oeis4.)