The signature of Γ+ 0(n)

Abstract

The signature of Γ+ 0(eN2), where e is square free, is completely determined if e=3 or N is odd or e∈Ψ, where Ψ is the set of all square free integers e∈N such that (i) if is odd, then admits no divisors of the form 8+3, (ii) if is even, then admits no divisors of the form 8+7.In particular, v2 (number of elliptic classes of period 2 of Γ+ 0(n)) is expressed as a linear combination of multiplicative functions. © 2001 Academic Press.