Atlas › Modular forms › Weight 4 › Level 21 › 21.4.a › 21.4.a.b

Newform orbit 21.4.a.b

$q$ -expansion

$q + 4q^{2} - 3q^{3} + 8q^{4} - 4q^{5} - 12q^{6} - 7q^{7} + 9q^{9} - 16q^{10} + 62q^{11} - 24q^{12} - 62q^{13} - 28q^{14} + 12q^{15} - 64q^{16} + 84q^{17} + 36q^{18} + 100q^{19} - 32q^{20} + 21q^{21} + 248q^{22} - 42q^{23} + O(q^{25})$

Coefficient field

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

$x$

Atkin–Lehner signs

$p$	$w_p$
3	$+1$
7	$+1$

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 even 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
$\operatorname{tr} a_p$	4	−3	−4	−7	62	−62	84	100	−42	−10	−48	−246	−248	68	324	258	120	622	904	−678	−642	740	468	200	−1266

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

Sato–Tate

The normalized $a_p / 2p^{3/2}$ for the primes $p < 1000$ not dividing 21, against the semicircle $\tfrac{2}{\pi}\sqrt{1 - x^2}$ :

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.096 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 engine's checks

dim M^+ at levels [1, 3, 7, 21]: [1, 2, 3, 10] (certified at ell = 2147483647)
T = [(2, 1), (5, 1)]; h of degree 4 = 1 x 4 (phi(ord eps) x dim S_k^new); 1 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(21, 4)[1]   # 21.4.a.b

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

cargo run --release -p sagebrush-web --example atlas -- 21:4 1000