[seqfan] A075346

[Frank Adams-Watters]

This sequence,

https://oeis.org/A075345

"Group the natural numbers such that the n-th group contains n terms and the group sum is the smallest possible prime: (2), (1, 4), (3, 5, 9), (6, 7, 8, 10), (11, 12, 13, 14, 17), (15, 16, 18, 19, 20, 21), ... Sequence gives group sums."

is not uniquely defined. For example, the third group could be 3, 6, 8 instead of 3, 5, 9. It looks to me like it is taking the first n-1 unused terms, and then adjusting the next term to get the smallest available prime.

Franklin T. Adams-Watters