Question
What are the missing numbers?
1801, 1851, (a)         , 1951, (b)         , 2051
2 m
(a)

Click button first when a symbol is required. X

(b)

Click button first when a symbol is required. X

What are the missing numbers?
1801, 1851, (a)         , 1951, (b)         , 2051