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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A091730 Norms of irreducible elements of Z[sqrt(-5)]. 2
 4, 5, 6, 9, 14, 21, 29, 41, 46, 49, 61, 69, 86, 89, 94, 101, 109, 121, 129, 134, 141, 149, 161, 166, 169, 181, 201, 206, 214, 229, 241, 249, 254, 269, 281, 289, 301, 309, 321, 326, 329, 334, 349, 361, 381, 389, 401, 409, 421, 446, 449, 454, 461, 469, 489 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS The following lists the types of numbers which appear (p,q are distinct primes, congruences are mod 20 and the number in square brackets gives the number of irreducible elements of that norm counting a and -a only once): 4 [1]; 5 [1]; p==1,9 [2]; p^2 where p==-1,-3,-7,-9 [1]; 2p where p==3,7 [2]; p^2 where p==3,7 [3]; pq where p,q==3,7 [4]. REFERENCES David A. Cox, Primes of the form x^2+ny^2, Wiley, 1989. A. Frohlich and M. J. Taylor, Algebraic number theory, Cambridge university press, 1991. LINKS Table of n, a(n) for n=0..54. CROSSREFS Sequence in context: A039013 A241511 A020669 * A058076 A238712 A033819 Adjacent sequences: A091727 A091728 A091729 * A091731 A091732 A091733 KEYWORD easy,nonn AUTHOR Paul Boddington, Feb 02 2004 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.

Last modified June 20 23:18 EDT 2024. Contains 373535 sequences. (Running on oeis4.)