Atlas › Modular forms › Weight 2 › Level 387 › 387.2.a › 387.2.a.b

Newform orbit 387.2.a.b

$q$ -expansion

$q - q^{2} - q^{4} + q^{5} - 3q^{7} + 3q^{8} - q^{10} + 3q^{11} - 5q^{13} + 3q^{14} - q^{16} - 6q^{17} + q^{19} - q^{20} - 3q^{22} - 8q^{23} + O(q^{25})$

Coefficient field

The coefficients $a_n$ generate $\mathbb{Q}$ . The eigenvalue of $T = T_{2} + 3T_{5}$ is a root of

$x - 2$

Atkin–Lehner signs

$p$	$w_p$
3	— ( $3^2 \mid 387$ )
43	$+1$

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 387.b (Cremona's 387c). Its optimal curve 387c1 is

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

of rank 1 with torsion of order 1. 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	−3	3	−5	−6	1	−8	9	−4	−6	−8	−1	−1	8	0	−10	12	−2	2	10	15	−2	−11

$\operatorname{tr} a_n$ 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 387, against the semicircle $\tfrac{2}{\pi}\sqrt{1 - x^2}$ :

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.2 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, 9, 43, 129, 387]: [0, 1, 2, 4, 16, 46] (certified at ell = 2147483647)
T = [(2, 1), (5, 3)]; h of degree 18 = 1 x 18 (phi(ord eps) x dim S_k^new); 3 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(387, 2)[1]   # 387.2.a.b

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

cargo run --release -p sagebrush-web --example atlas -- 387:2 1000