A380335 Minimal number of generators of Gamma_0(n).

2, 2, 2, 3, 3, 4, 3, 4, 4, 5, 4, 6, 5, 6, 6, 6, 5, 8, 5, 8, 7, 8, 6, 10, 7, 9, 8, 10, 7, 14, 7, 10, 10, 11, 10, 14, 9, 12, 11, 14, 9, 18, 9, 14, 14, 14, 10, 18, 11, 17, 14, 16, 11, 20, 14, 18, 15, 17, 12, 26, 13, 18, 18, 18, 17, 26, 13, 20, 18, 26, 14, 26, 15, 21, 22, 22, 18, 30

Offset

1,1

Links

Table of n, a(n) for n=1..78.

Example

For n=1 the generators are S and T, so a(1)=2.
For n=2 they are [1 1][0 1], [1 -1][2 -1], so a(2)=2.

Prog

(SageMath) [len(Gamma0(N).generators()) for N in range(1, 100)]

Crossrefs

Cf. A001615.

Sequence in context: A107325 A003050 A070868 * A342219 A272612 A155216

Adjacent sequences: A380332 A380333 A380334 * A380336 A380337 A380338

Keyword

nonn

Author

Abouzar Shirazi, Jan 21 2025

Status

approved