Cannot delete partition (minus greyed out) - non-encrypted, no core storage

Question

When trying to install Windows 10 from scratch on my Late 2013 MacBook Pro, I was unable to remove the old BOOTCAMP partition through the Boot Camp Assistant. I erased the partition with Disk Utility, but was unable to join it with my main partition. Now when I run Boot Camp Assistant, I get the following message: "The startup disk cannot be partitioned or restored to a single partition."

Running diskutil core storage list returns: No CoreStorage logical volume groups found

Additionally, FileVault is turned off.

I can add new partitions to the drive manually and delete them, but every time I try to resize the main partition it adds a new Untitled partition that is not deleteable (minus button is greyed out). Any ideas?

$ sudo gpt -r show /dev/disk0
      start       size  index  contents
          0          1         PMBR
          1          1         Pri GPT header
          2         32         Pri GPT table
         34          6         
         40     409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
     409640  244140624      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  244550264    1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
  245819800       1640         
  245821440   10921976      4  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  256743416     262144         
  257005560   10920264      5  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  267925824     262144         
  268187968  221784600      6  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  489972568     262151         
  490234719         32         Sec GPT table
  490234751          1         Sec GPT header

Answer 1

Ok, I figured out an alternative method - I was able to combine the partitions using the diskutil mergePartitions command (e.g. diskutil mergePartitions JHFS+ MacHD disk0s2 disk0s4). Hope that helps anyone else with the same issue!