  In this note we study holomorphic integer graded vertex superalgebras. We
prove that all such vertex superalgebras of central charge 8 and 16 are purely
even. For the case of central charge 24 we prove that the weight-one Lie
superalgebra is either zero, of superdimension 24, or else is one of an
explicit list of 1332 semisimple Lie superalgebras.
