What is the missing number in the sequence 9-61-52-63-94- - 18?

Answer 1

46.

It's the square numbers with their digits reversed:

9 → 9 = 32

61 → 16 = 42

52 → 25 = 52

63 → 36 = 62

94 → 49 = 72

???

18 → 81 = 92

The missing number is the square of 8 with its digits reversed:

82 = 64 → 46.