### Brain Teasers

# 1, 3, 7, 11, 17, 23, 31, 50, 60, 71, ...

What are the next five terms in this sequence?

1, 3, 7, 11, 17, 23, 31, 50, 60, 71, 83, 97, 111, 127, 153, 171, 190, 210, 231, 263, 287, 311, 337, 373, ___, ___, ___, ___, ___, ...

1, 3, 7, 11, 17, 23, 31, 50, 60, 71, 83, 97, 111, 127, 153, 171, 190, 210, 231, 263, 287, 311, 337, 373, ___, ___, ___, ___, ___, ...

### Hint

1111, 11111, 111111, ... will also appear in this sequence.### Answer

501, 530, 570, 601, 633.In all the natural numbers that don't contain the "unlucky" digit 4, the first one is 1, skip one and get 3, skip two and get 7, skip three and get 11, and so on.

It can also be said that these are the triangular numbers in the nonary system, except that the digits 0, 1, 2, 3, 5, 6, 7, 8, 9 are being used to represent 0, 1, 2, 3, 4, 5, 6, 7, 8.

Hide Hint Show Hint Hide Answer Show Answer

## What Next?

**Solve a Similar Brain Teaser...**

Or, get a random brain teaser.

If you become a registered user you can vote on this brain teaser, keep track of

which ones you have seen, and even make your own.

## Comments

could u explain that again please???

I don't get it.

uh..

say wha?

what the eff??

how is four unlucky. this is for someone with advanced knowledge of math.

## Follow Braingle!