Qm
Brainteasers

77, 49, 36, 18, what next?

sequencesdigitspatterns

Find the rule and the next term of

77, 49, 36, 18, ?

Each term comes from the previous one by a simple operation on its digits. After you find the rule, say what happens if you keep applying it, and whether every starting number eventually behaves the same way.

Show a hint

7 times 7 is 49.

Your answer

Solving needs a free account

Answers, streaks and solutions unlock when you are signed in. Reading the question and the hint stays free.

Create a free accountSign in

Discussion

Sign in to join the discussion · reading is open to everyone

💡 Discussion rules

  1. No full solutions here. Hints and approaches only.
  2. Complexity, edge cases and intuition are the point.
  3. Interview experiences are welcome. Respect your NDAs.

Loading discussion…

Learn the concepts

The theory behind this question.

Generating Functions as a Puzzle ToolThe Harmonic Series in PuzzlesThe Look-and-Say SequenceHow to Crack a What-Comes-Next QuestionTribonacci Numbers and Tiling Counts

Related questions

1, 4, 9, 61, 52, 63, 94, what next?The sequence that describes its own runs10, 11, 12, 13, 14, 20, 22, 101, what next?The number equal to the sum of the cubes of its digitsThe book that took 792 digits to number
All questions →