Atlas › Modular forms › Weight 2 › Level 867 › 867.2.a › 867.2.a.a

Newform orbit 867.2.a.a

$q$ -expansion

$q - q^{2} - q^{3} - q^{4} + q^{6} - 4q^{7} + 3q^{8} + q^{9} + 4q^{11} + q^{12} + 2q^{13} + 4q^{14} - q^{16} - q^{18} + 4q^{19} + 4q^{21} - 4q^{22} - 4q^{23} - 3q^{24} + O(q^{25})$

Coefficient field

The coefficients $a_n$ generate $\mathbb{Q}$ . The eigenvalue of $T = T_{2} + 2T_{5} + 3T_{7} + 4T_{11} + 5T_{13} + 6T_{19} + 7T_{23} + 8T_{29}$ is a root of

$x - 9$

Atkin–Lehner signs

$p$	$w_p$
3	$+1$
17	— ( $17^2 \mid 867$ )

For $p \parallel N$ every form in the orbit has $a_p = -p^{k/2-1} w_p$ .

Elliptic curve

By modularity this newform is the one attached to the isogeny class 867.a (Cremona's 867b). Its optimal curve 867b1 is

$y^2 + xy + y = x^3 + x^2 - 23x + 20$

of rank 1 with torsion of order 2. Its $a_p$ , computed by Sagebrush's point-counting engine, equal the newform's for every prime $p < 1000$ .

Traces of Hecke eigenvalues

$p$	2	3	5	7	11	13	17	19	23	29	31	37	41	43	47	53	59	61	67	71	73	79	83	89	97
$\operatorname{tr} a_p$	−1	−1	0	−4	4	2	0	4	−4	0	4	−8	−8	4	−8	−6	12	−8	12	−12	0	−4	−12	−10	−16

$\operatorname{tr} a_n$ for every $n \le 1000$ is in the JSON.

Sato–Tate

The normalized $a_p / 2p^{1/2}$ for the primes $p < 1000$ not dividing 867, against the semicircle $\tfrac{2}{\pi}\sqrt{1 - x^2}$ :

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.671 s (one thread) and proven: the dimensions are certified, and the characteristic polynomial of $T$ over $\mathbb{Z}$ is reconstructed by CRT past a rigorous coefficient bound. The label, dimension and $\operatorname{tr} a_p$ for every $p < 1000$ equal LMFDB's.

The engine's checks

dim M^+ at levels [1, 3, 17, 51, 289, 867]: [0, 1, 2, 8, 26, 104] (certified at ell = 2147483249)
T = [(2, 1), (5, 2), (7, 3), (11, 4), (13, 5), (19, 6), (23, 7), (29, 8)]; h of degree 45 = 1 x 45 (phi(ord eps) x dim S_k^new); 13 primes, 0 rejected

Open in the notebook · JSON · stored data

Recompute it yourself

In Sage mode at sagebrush.space (or npx sagebrush --sage):

newform_orbits(867, 2)[0]   # 867.2.a.a

With the Rust engine (source), in engine/:

cargo run --release -p sagebrush-web --example atlas -- 867:2 1000