Atlas › Modular forms › Weight 2 › Level 218 › 218.2.a › 218.2.a.b

Newform orbit 218.2.a.b

Trace form

The 2 newforms in this orbit are conjugate over $\mathbb{Q}$ ; the sum of their $q$ -expansions is

$2q - 2q^{2} - 4q^{3} + 2q^{4} + 2q^{5} + 4q^{6} - 4q^{7} - 2q^{8} + 6q^{9} - 2q^{10} - 2q^{11} - 4q^{12} - 8q^{13} + 4q^{14} - 8q^{15} + 2q^{16} - 4q^{17} - 6q^{18} - 10q^{19} + 2q^{20} + 4q^{21} + 2q^{22} - 2q^{23} + 4q^{24} + O(q^{25})$

Coefficient field

The coefficients $a_n$ generate $\mathbb{Q}(\sqrt{2})$ . It is generated by the eigenvalue $\alpha$ of $T = T_{3} + 3T_{5}$ , whose minimal polynomial is

$x^{2} - 2x - 7$

Atkin–Lehner signs

$p$	$w_p$
2	$+1$
109	$+1$

For $p \parallel N$ every form in the orbit has $a_p = -p^{k/2-1} w_p$ . The Fricke sign is $w_N = +1$ , so the sign of the functional equation is $(-1)^{k/2} w_N = -1$ : each L-function in the orbit has odd analytic rank.

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
$\operatorname{tr} a_p$	−2	−4	2	−4	−2	−8	−4	−10	−2	6	−4	−4	8	−4	6	8	−4	2	4	4	−26	4	4	14	18

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

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.274 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, 2, 109, 218]: [0, 1, 9, 29] (certified at ell = 2147482801)
T = [(3, 1), (5, 3)]; h of degree 10 = 1 x 10 (phi(ord eps) x dim S_k^new); 2 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(218, 2)[1]   # 218.2.a.b

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

cargo run --release -p sagebrush-web --example atlas -- 218:2 1000