BUG: fix indexing of harmonic coefficients (for good?)
BUG: fix indexing of harmonic coefficients (for good?)

ceholden/yatsm,jmorton/yatsm,valpasq/yatsm,valpasq/yatsm,c11/yatsm,ceholden/yatsm,c11/yatsm,jmorton/yatsm,jmorton/yatsm