The Index Function in Sheets appears to have a bug. It seems you cannot index the same column or row that the calculated cell is in. The suggested result when typing the function is correct, but when the function is entered, it returns "Error, circular dependency detected."

Examples:

Value in cell A1 --> 20

Function in cell A2 --> =INDEX(A:A, row() - 1) (suggestion shows 20)

Actual Result
Value in A2 --> "Error, circular dependency detected"

Expected Result (works in Excel and Google Sheets)
Value in A2 --> 20

Value in cell E10 --> 15

Function in cell F10 --> =INDEX(A10:R10, column() - 1) (suggestion shows 15)

Actual Result
Value in F10 --> "Error, circular dependency detected"

Expected Result (works in Excel and Google Sheets)
Value in F10 --> 15