This sequence is complete (cannot be extended in any direction), however, two numbers don't fit. Which two?

15 68 53 8 66 6 73 5 57


1 Answer 1



66, 57


Converting to element symbols we get P, Er, I, O, Dy, C, Ta, B, La. This almost spells out Periodic Table, but the two errors are 66 and 57 (and unfortunately cannot be corrected because no element has symbol Di or Le (and another spacing won't help either)

  • 1
    $\begingroup$ Obviously correct $\endgroup$
    – FIreCase
    Mar 14, 2020 at 22:05

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.