-1
$\begingroup$

Is this series complete, using '0' is not allowed:

$6 = 6$ or $5+1$ or $1+5$ or $4+2$ or $2+4$ or $3+3$ or $4+1+1$ or $1+4+1$ or $1+1+4$ or $1+2+3$ or $1+3+2$ or $2+3+1$ or $2+1+3$ or $3+1+2$ or $3+2+1$ or $1+1+1+3$ or $1+1+3+1$ or $1+3+1+1$ or $3+1+1+1$ or $1+1+1+1+2$ or $1+1+1+2+1$ or $1+1+2+1+1$ or $1+2+1+1+1$ or $2+1+1+1+1$ or $1+1+1+1+1+1$

5 = 5 or 4+1 or 1+4 or 3+2 or 2+3 or 1+1+3 or 3+1+1 or 1+3+1 or 1+2+2 or 2+1+2 or 2+2+1 or 2+1+1+1 or 1+2+1+1 or 1+1+2+1 or 1+1+1+2 or 1+1+1+1+1

4 = 4 or 3+1 or 2+2 or 1+3 or 1+1+2 or 1+2+1 or 2+1+1 or 1+1+1+1

3 = 3 or 1+1+1 or 1+2 or 2+1

2 = 2 or 1+1

1 = 1

The number of partitions in this series is 1,2,4,8,16,25.

Have I missed any, as 25 seems odd to me.

$\endgroup$
  • $\begingroup$ 2+2+2 has been missed. There are 6 others. In total, there are 32. $\endgroup$ – S.C.B. May 9 '16 at 15:50
3
$\begingroup$

You have missed seven ways. Mainly, $$2+2+2=6$$$$1+1+2+2=6$$$$1+2+1+2=6$$$$1+2+2+1=6$$$$2+1+2+1=6$$$$2+2+1+1=6$$$$2+1+1+2=6$$So there are $32$ ways. However, one thing worth mentioning is that your definition strays from the normal definition of partitions, where two sums that differ only in the order of their summands are considered the same partition. In fact, if the order matters, as in your case, the correct term is a composition.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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