https://lmaowisc.r-universe.dev/grpseqhttps://lmaowisc.r-universe.dev/api/packages/grpseqhttps://lmaowisc.r-universe.dev/grpseq/grpseq.pdfhttps://lmaowisc.r-universe.dev/grpseq/doc/manual.htmlhttps://lmaowisc.r-universe.dev/grpseq/citationhttps://lmaowisc.r-universe.dev/grpseq/citation.txthttps://lmaowisc.r-universe.dev/grpseq/citation.cffhttps://lmaowisc.r-universe.dev/grpseq/doc/futility_design.Rmdhttps://lmaowisc.r-universe.dev/articles/grpseq/futility_design.html