The beta family at the prime two and modular forms of level three.

link: http://arxiv.org/abs/0912.3082
Abstract

We use the orientation underlying the Hirzebruch genus of level three to map
the beta family at the prime p=2 into the ring of divided congruences. This
procedure, which may be thought of as the elliptic greek letter beta
construction, yields the f-invariants of this family.