Atlas › Modular forms › Weight 2 › Level 855 › 855.2.a › 855.2.a.c

Newform orbit 855.2.a.c

$q$ -expansion

$q + q^{2} - q^{4} + q^{5} - 2q^{7} - 3q^{8} + q^{10} + 6q^{11} - 2q^{14} - q^{16} + 6q^{17} + q^{19} - q^{20} + 6q^{22} + 8q^{23} + O(q^{25})$

Coefficient field

The coefficients $a_n$ generate $\mathbb{Q}$ . The eigenvalue of $T = T_{2} + 2T_{7} + 3T_{11} + 4T_{13} + 5T_{17} + 6T_{23} + 7T_{29} + 8T_{31}$ is a root of

$x - 65$

Atkin–Lehner signs

$p$	$w_p$
3	— ( $3^2 \mid 855$ )
5	$-1$
19	$-1$

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 855.c (Cremona's 855c). Its optimal curve 855c1 is

$y^2 + xy = x^3 - x^2 + 171x$

of rank 0 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	0	1	−2	6	0	6	1	8	−4	0	4	0	−2	8	−2	−12	2	−8	−16	14	8	0	0	−12

$\operatorname{tr} a_n$ 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 855, against the semicircle $\tfrac{2}{\pi}\sqrt{1 - x^2}$ :

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.739 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, 5, 9, 15, 19, 45, 57, 95, 171, 285, 855]: [0, 1, 1, 2, 4, 2, 8, 8, 12, 22, 44, 124] (certified at ell = 2147483629)
T = [(2, 1), (7, 2), (11, 3), (13, 4), (17, 5), (23, 6), (29, 7), (31, 8)]; h of degree 30 = 1 x 30 (phi(ord eps) x dim S_k^new); 9 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(855, 2)[2]   # 855.2.a.c

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

cargo run --release -p sagebrush-web --example atlas -- 855:2 1000