## Sequence 1, 3, 7, 12

Which is the next number in the following sequence:

1, 3, 7, 12, 18, 26, 35, 45, 56, ?

This is the so called Hofstadter Figure-Figure Sequence.

The sequence of the differences between the consecutive numbers in the original sequence is 2, 4, 5, 6, 8, 9, 10, 11â€¦ These are exactly the natural numbers missing from the original sequence. Therefore, the next number should be 56 + 13 = 69.

FEATURED

## Sequence 1, 11, 21, 1112

What follows next in the following sequence:

1, 11, 21, 1112, 3112, 211213, 312213, ?

Every term in the sequence describes how many 1s, 2s, 3s, etc. were there in the previous term. “11” means that in the previous term there was one 1. “21” means that in the previous term there were two 1s. “1112” means that in the previous term there were one 1 and one 2. “3112” means that in the previous term there were three 1s and one 2. “211213” means that in the previous term there were two 1s, one 2 and one 3. “312213” means that in the previous term there were three 1s, two 2s and one 3. Therefore, the next number in the sequence should be 212223.

## Sequence 4, 2, 3, 4

What is the next number in this sequence:

4, 2, 3, 4, 6, 2, 4, ?

The answer is 8. The numbers represent the lengths of the words in the question:

what â†’ 4
is â†’ 2
the â†’ 3
next â†’ 4
number â†’ 6
in â†’ 2
this â†’ 4
sequence â†’ 8

## The Next Letter

Which is the next letter in the following sequence:

S S E N T T T T T T T T T T T T T T T T T T T T ?

The answer is F. These are the first letters of the numbers Seventeen, Eighteen, Nineteen, Twenty, Twenty-one, and so on.

## The Next Die

Which die completes the following sequence:

If you look at dots in the top row, you will see that they are put together into groups of 1, 2, 3, 4, and so on.