# What number follows up next?

I'm currently working on a (difficult) number progression and need your help. How would you continue?

2, 5, 12, 25, 54, 113, 240, 481 ?

Thanks in forward!

• sorry had to edit it! After 54 it goes 113, 240, 481 Mar 17, 2018 at 2:51
• OEIS A063807 Mar 17, 2018 at 2:56

@OP: When posting number sequence puzzles, or when looking for the next number in a sequence, do check the Online Encyclopedia of Integer Sequences (OEIS) for the sequence. Many sequences are listed there, so the chances are you will often find what you're looking for there.

Posting this answer as a community wiki as it is unfair to gain reps off an OEIS sequence.

OEIS A063807 defines this as:

$a(0) = 0, \text{ and } a(n+1) = a(n) + (\text{next prime larger than } a(n))$.

For instance:
$$0+2=2$$ $$2+3=5$$ $$5+7=12$$ $$12+13=25$$ $$25+29=54$$ $$\cdots$$

Hence the sequence is $$0, 2, 5, 12, 25, 54, 113, 240, 481, 968, 1939, 3888$$

• Sorry got a little overexcited with the editing...never did one for a community wiki before :P Mar 17, 2018 at 3:06
• LOL :-) @NL628 and thanks for the formatting cleanup! Mar 17, 2018 at 3:07