=MOD(SUMPRODUCT(LEFT((0&MID(H3,ROW($1:$19),1))*2^MOD(ROW($1:$19)+MOD(LEN(H3),2),2),1)+(0&MID((0&MID(H3,ROW($1:$19),1))*2^MOD(ROW($1:$19)+MOD(LEN(H3),2),2),2,1))),10)=0