A091730 Norms of irreducible elements of Z[sqrt(-5)].

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

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