|
| |
|
|
A263849
|
|
Let R = Z((1+sqrt{5})/2) denote the ring of integers in the real quadratic number field of discriminant 5. Let nu in R be a totally positive element of norm m = A031363(n). Then a(n) is the number of ways of writing nu as a sum of three squares in R.
|
|
3
|
|
|
|
1, 6, 12, 24, 32, 24, 54, 24, 24, 30, 24, 48, 48, 96, 24, 48, 96, 48, 24, 120, 108, 48, 72, 48, 120, 54, 48, 48, 48, 84, 72, 120, 72, 78, 48, 144
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
0,2
|
|
|
COMMENTS
|
Let R = Z((1+sqrt{5})/2) denote the ring of integers in the real quadratic number field of discriminant 5. The main result of Maass (1941) is that every totally positive nu in R is a sum of 3 squares x^2+y^2+z^2 with x,y,z in R. The number N_{nu} of such representations is given by the formula in the theorem on page 191. The norms of the totally positive elements nu are rational integers m belonging to A031363, so we can order the terms of the sequence according to the values m = A031363(n). [Comment based on remarks from Gabriele Nebe.]
The terms were computed with the aid of Magma by David Durstoff, Nov 11 2015.
The attached file from David Durstoff gives list of pairs m=A031363(n), a(n), and also the initial terms of Maass's series theta(tau). David Durstoff says: "I expressed theta(tau) in terms of two variables q1 and q2. The coefficient of q1^k q2^m is a(nu) with k = trace(nu/delta) and m = trace(nu), where delta = (5+sqrt{5})/2 is a generator of the different ideal. I computed the terms for q1^0 to q1^10 and all possible powers of q2."
|
|
|
REFERENCES
|
Maass, Hans. Über die Darstellung total positiver Zahlen des Körpers R (sqrt(5)) als Summe von drei Quadraten, Abhandlungen aus dem Mathematischen Seminar der Universität Hamburg. Vol. 14. No. 1, pp. 185-191, 1941.
|
|
|
LINKS
|
|
|
|
CROSSREFS
|
See A263850 for another version of this sequence.
|
|
|
KEYWORD
|
nonn,more
|
|
|
AUTHOR
|
|
|
|
STATUS
|
approved
|
| |
|
|
