Miscellaneous quizzes.

 Spoiler

1, 5, 9, 17, 27, 33, 51, 65,.. X

as said, hint is a palidrome

17+33 = 50
9+51 = 60
5+65 = 70


therefor, 1+X should be 80
80-1= 79

answer is 79

wow, i had the same answer a different way, but that works too

Doesn't work if the list goes longer though, I simply cut it there for convenience. Good guess though.

EDIT: try my 3rd one, a bit harder than yours.