遇數字 遞增 減 (10280)

B2=IF(A2,A2,IFERROR(TEXT(LOOKUP(1,0/(B$1:B1<>""),B$1:B1)-1,"0;;"),""))

另解 B2=IFERROR(TEXT(LOOKUP(99,A$1:A2)-ROW()+LOOKUP(99,A$1:A2,ROW($1:2)),"0;;"),"")

另解 B2=IF(A2,A2,IF(IFERROR(B1-1,0)>0,B1-1,""))

利用B列 C2=IF(A2,1,IF(B2="","",C1+1))